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1
Brown, Simon Mark. "Neutron shell breaking in neutron-rich neon isotopes." Thesis, University of Surrey, 2010. http://epubs.surrey.ac.uk/2829/.
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The breaking of the N=20 shell gap in neutron-rich nuclei is investigated by studying the single-particle structure of 27Ne via neutron transfer onto a 26Ne beam. The observation of low-lying negative parity states in 27Ne above the 3/2+ ground state is further evidence of the raising of the νd3/2 orbital that is seen in other neutron-rich nuclei in the N=20 region. The previously unseen 7/2− state has been identified as unbound by 331 keV and lies above the already known 3/2− level. The measurements of the present work contradict SDPF-M Monte-Carlo Shell Model predictions, but are in good agreement with WBP shell model calculations in which the single-particle energies of the pf shell are artificially lowered by 1 MeV. This modification was made to mimic the closing of the N = 20 shell gap in neutron-rich nuclei. The predictions of the modifiedWBP calculations are also in agreement with experimental measurements in the adjacent nuclei of 25Ne and 29Mg. The calculations show that core-excited configurations play a significant role in both the 3/2+ ground state and the 7/2− intruder state in 27Ne.
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González, Boquera Claudia. "Neutron-rich matter in atomic nuclei and neutron stars." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/668774.
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The proper understanding of the equation of state (EoS) of highly asymmetric nuclear matter is essential when studying systems such as neutron stars (NSs). Using zero-range Skyrme interactions and finite-range interactions such as Gogny forces, momentum-dependent interactions (MDI) and simple effective interactions (SEI), we analyze the properties of the EoS and the influence they may have on the calculations for NSs.
We start by studying the convergence properties of the Taylor series expansion of EoS in powers of the isospin asymmetry. Next, we analyze the accuracy of the results for β-stable nuclear matter, which is found in the interior of NSs, when it is computed using the Taylor expansion of the EoS. The agreement with the results obtained using the full expression of the EoS is better for interactions with small-to-moderate values of the slope of the symmetry energy L.
The mass and radius relation for a NS is obtained by integrating the so-called Tolman-Oppenheimer-Volkoff (TOV) equations, where the input is the EoS of the system. We have studied the mass-radius relation for Skyrme and Gogny interactions, and we see that that very soft forces are not able to give stable solutions of the TOV equations and only the stiff enough parametrizations can provide 2M0 NSs. We also notice that none of the existing parametrizations of the standard Gogny D1 interaction is able to provide a NS inside the observational constraints. Because of that, we propose a new parametrization, which we name D1M∗, that is able to provide NSs of 2M0 while still providing the same good description of finite nuclei as D1M. A parametrization D1M∗∗ is also presented, which is fitted in the same way as D1M∗ and provides NSs up to 1.91M0.
Moreover, we estimate the core-crust transition in NSs by finding where the nuclear matter in the core is unstable against fluctuations of the density. To do that, we employ two methods, the thermodynamical method and the dynamical method. In the case of finite-range interactions, such as the Gogny ones, to use the dynamical method we have had to derive the explicit expression of the energy curvature matrix in momentum space for this type of interactions. We observe a decreasing trend of the transition density with the slope L of the symmetry energy, while the correlation between the transition pressure and L is much lower.
Finally different NS properties are studied. The crustal properties, such as the crustal mass, crustal thickness and crustal fraction of the moment of inertial have lower values if one computes them using the core-crust transition density obtained with the dynamical method instead of the one obtained with the thermodynamical method, pointing out the importance of the accurate evaluation of the transition density when studying observational phenomena. We have also studied the moment of inertia of NSs, which is compared to constraints proposed in the literature. Finally, the tidal deformability for NSs is also calculated and compared with the constraints coming from the GW170817 event detected by the LIGO and Virgo observatories and which accounts for the merger of two NSs in a binary system.El coneixement de l’equació d’estat (EoS) de matèria altament densa i assimètrica és essencial per tal d’estudiar les estrelles de neutrons (NSs). En aquesta tesi s’analitzen, utilitzant interaccions de camp mig no relativistes, les propietats de l’EoS i la seva influència en càlculs de NSs. Primerament, s’estudia la convergència del desenvolupament en sèrie de Taylor de l’EoS en potències de l'assimetria d’isospí. Seguidament, s’analitza l’exactitud dels resultats per matèria β-estable, la qual es troba a l’interior de les NSs, quan es calcula utilitzant el desenvolupament de Taylor de l’EoS. La relació entre la massa i el radi obtinguda integrant les equacions Tolman-Oppenheimer-Volkoff (TOV) també és estudiada. A causa de que les interaccions de Gogny de la família D1 no aconsegueixen donar NSs compatibles amb observacions astrofísiques, en aquesta tesi proposem dues noves forces de Gogny, anomenades D1M∗ i D1M∗∗, les quals poden donar, respectivament, NSs de 2 i 1.91 masses solars. Una altra part de la tesi es dedica a l’estudi de la transició entre l’escorça i el nucli, buscant la densitat a la qual la matèria uniforme al nucli és inestable contra fluctuacions de densitat. Ho estudiem amb dos mètodes, el mètode termodinàmic i el mètode dinàmic. Finalment, s’analitzen diverses propietats de les NSs, com són la relació entre la massa i el radi de l’estrella, les propietats de l’escorça, el moment d’inèrcia, així com la deformació deguda als corrents de marea (tidal deformability) que està relacionada amb l’emissió d’ones gravitacionals en sistemes binaris d’estrelles de neutrons.
3
Reed, Alan Thomas. "Decay studies of neutron-rich nuclei." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367175.
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Gengelbach, Aila. "Collectivity in Neutron-Rich Erbium Isotopes." Licentiate thesis, Uppsala universitet, Kärnfysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-442208.
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Neutron-rich rare-earth nuclei around the maximum of collectivity are predicted to exist with an extremely stable intrinsic configuration in their ground-state structure. Due to the high degree of axial symmetry and large deformation, these nuclei are also excellent candidates for having long-lived high-K isomers. The present work concerns a study of the structure of the yrast bands and a search for isomers in the neutron-rich 68Er isotopes. Excited states of 68Er isotopes were populated via multi-nucleon transfer reactions. A 859 MeV 136Xe-beam was used to bombard a 170Er-target. The experimental setup consisted of the high-resolution γ-ray spectrometer AGATA coupled to the heavy-ion magnetic spectrometer PRISMA. The experiment collected 2 TB of useful data corresponding to 3 days of effective beam time. Beam-like fragments were identified by the PRISMA specrometer placed at the grazing angle of 44 degrees. PRISMA allows for Z, A and q identification as well as TOF and velocity vector determination. This is required for the Doppler correction of the emitted γ rays detected in time coincidence with AGATA. A good Z and very clean A separation has been achieved in PRISMA. Making use of two-body kinematics, Doppler corrected γ-ray spectra for target-like fragments were obtained as well. Due to the novel techniques of PSA and γ-ray tracking, AGATA provided high-quality γ-ray spectra for both beam-like xenon and target-like erbium isotopes. Known yrast bands and isomeric states in neutron-rich erbium isotopes were observed. A candidate for the decay of an isomeric state with Eγ=184 keV in 173Er, which has no previously known excited states, was identified.
5
Woods, P. J. "Mass measurements of light neutron rich nuclei." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374579.
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Rueffer, Mareike. "Collinear laser spectroscopy of neutron-rich niobium." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/802/.
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Hyperfine structure spectra and isotope shifts of the neutron-rich nuclei \(^{99}\)Nb, \(^{101}\)Nb, \(^{102}\)Nb and \(^{103}\)Nb were obtained at the IGISOL (Ion Guide Isotope Separator On-Line) facility at the accelerator laboratory of the University of Jyväskylä. The data were taken using collinear laser spectroscopy of bunched beams. Optical pumping from the ground state to populate metastable atomic states in the ion beam cooler allowed efficient spectroscopy of the ionic system that would otherwise be inaccessible due to a lack of suitable ground state resonance lines. The measurements of the hyperfine structure and the isotope shifts contribute valuable nuclear information to the understanding of the \(A\) ~ 100 region which displays a sudden onset of deformation that cannot be explained by the single particle shell model. It was possible to confirm the spin assignments for \(^{99}\)Nb, \(^{101}\)Nb and \(^{103}\)Nb as \(I\) = 9/2, \(I\) = 5/2 and \(I\) = 5/2 respectively. The extracted information on the mean square charge radii, \(\delta\big
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Patel, Dinesh. "Magnetic properties of neutron-rich fission fragments." Thesis, University of Manchester, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.756107.
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Pietras, Ben. "Spectroscopy of neutron-rich oxygen and fluorine nuclei via single-neutron knockout reactions." Thesis, University of Liverpool, 2009. http://livrepository.liverpool.ac.uk/3713/.
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At the limits of nuclear stability, increasing proton-neutron asymmetry leads to a shifting of orbitals from nuclear shell model predictions. In turn this leads to a weakening of shell gaps such as at N = 20, and the emergence of new gaps at N = 14 and 16. To observe this evolution of the structure as the neutron dripline is approached, single-nucleon removal reactions have been employed for oxygen and fluorine isotopes. These reactions are an excellent way of probing the nuclear wavefunction to reveal information on the single-particle content in the wavefunction. Cross sections have been measured, both inclusive and exclusive, and partial production cross sections calculated. This has allowed spectroscopic factors to be extracted and compared to theoretical predictions from shell model calculations. Longitudinal momentum distributions, both inclusive and exclusive, have also been measured. The orbital angular momentum of the removed nucleon has a pronounced effect on the momentum distribution of the surviving core, which can be compared to theoretical predictions based on eikonal theory. This gives a valuable insight into the configuration mixing for the ground and excited states of the nuclei of interest.
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O'Donnell, David. "γ-Ray spectroscopy of neutron-rich chlorine nuclei." Thesis, University of the West of Scotland, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556205.
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A beam of 36/16S20 at 215 MeV was used to bombard a 300 ugcm-2 thick target of 208/82Pb126 in order to initiate deep-inelastic and multi-nucleon transfer reactions. The I-ray decay of the reaction products was studied using the CLARA array of escape suppressed germanium detectors which was coupled to the large-angular-acceptance magnetic spectrometer PRISMA, in which the velocity, mass, atomic number and kinetic energy of the reaction products was measured. Determination of the velocity and mass has allowed Doppler corrected γ-ray spectra to be obtained for each individual projectile-like nuclide to be produced. Seven neutron-rich isotopes of Cl have been populated and their decay by γ-ray emission has been studied. Decay schemes have been constructed and compared to the results of shell-model calculations. Previously unreported transitions have been observed in 38Cl, 40Cl, 41Cl and 42Cl. ___.
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Valiente-Dobon, Jose Javier. "Studies of neutron-rich nuclei using deep inelastic collisions." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/843390/.
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A deep inelastic reaction between a thin self-supporting 19878Pt target and an 850MeV 13654Xe beam has been used to populate and study both neutron-rich nuclei around the beam and target masses and the reaction mechanism. An Ipi= 10+ isomeric state has been found in the N = 80 isotone 13656Ba with a measured half-life of 91 +/- 2ns. The structure of the predominantly (h11/2)-210+ isomer is discussed in terms of shell model and pair-truncated shell model calculations and compared to the even-Z, N = 80 isotones ranging from 13050Sn to 14868Er. A qualitative explanation of the observed dramatic decrease in the B(E2 : 10+ → 8+) value for the N = 80 isotones at 136Ba is given in terms of the increasing single-particle energy of the h11/2 neutron configuration as the proton sub-shell is filled. A 4-quasiparticle isomer has been observed in with a half-life of 188 +/- 38ns. The results are compared with blocked BCS Nilsson calculations which favour the Kpi= 15- interpretation. This isomer completes the even-A tungsten, 4-quasiparticle isomer systematics from A = 176 to 186. A high spin isomeric state has been found in the near spherical nucleus 19874W with a half-life of 36 +/- 2ns. The nature of this isomer has been interpreted from an examination of the systematics of platinum isotopes and neighbouring nuclei as a tentative Ipi= 12+ state from rotation-aligned, two neutron (i13/2)2configuration. Using prompt-delayed gamma-ray correlations, the complementary fragments of the reaction have been studied and used to identify new states in 19476Os. The angular momentum transfer to the binary fragments in the reaction has been investigated in terms of the average total gamma-ray fold versus the scattering angle of the recoils.
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Regina, Jenny. "Identication of Neutron-Rich Xe-Isotopes in PRISMA+AGATA Data." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-202167.
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The purpose of this project was to analyze data from an experiment carried out at LNL (Legnaro National Laboratories) in order to test the collective nuclear model. In the experiment 170Dy was created by multi-nucleon transfer reactions. This isotope is predicted to be the most collective of all nuclei with A < 190. γ-ray energies originating from its deexcitation allow to measure its collectivity. The PRISMA spectrometer was used to determine which ions were produced in the reactions and AGATA measured the γ-radiation from these products. The analysis consists of a calibration process of all detectors and eventually leads to the identication of 170Dy and of its deexcitation energies. This report explains the analysis procedure and some of the steps to identify the reaction prodcuts and corresponding γ-ray energies were performed. Xe-isotopes and corresponding γ-spectra have been identied.
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Liang, Xiaoying. "Spectroscopy of neutron rich nuclei produced in deep inelastic processes." Thesis, University of the West of Scotland, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246342.
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Steer, Steven John. "Isomer decay spectroscopy of N<126 neutron-rich nuclei." Thesis, University of Surrey, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493243.
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Caamano, Monica. "New isomers in the neutron-rich A~190 mass region." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/844621/.
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Previously unobserved isomeric states in 188Ta,190W, 192Re, 193Re, 195Os, 197Ir, 198Ir, 200Pt, 201Pt, 202Pt and 203Au, with half-lives ranging from 10 ns to 290 mus have been populated and studied using a fragmentation reaction in conjunction with a forward focussing spectrometer. In most cases, this provided the first ever spectroscopic data made available for the nucleus, and 200Pt presented the first new seniority 4 state, on the basis of gamma-gamma coincidences, following a fragmentation reaction. Half-lives have been measured and tentative level schemes have been drawn for each isomer, spins and parities being consistent with blocked BCS calculations, hindrance factors, systematics and the relative intensities of gamma-rays and X-rays (where possible). Isomeric ratios have been measured, values ranging from 1 % to 64 %. Potential Energy Surface calculations were performed in parallel to the blocked BCS calculations, in order to provide deformation parameters, excitation energies and quasiparticle configurations. Ground state (or lowest level) shape calculations reveal a change from axially symmetric, through triaxial, to spherical shapes across the data set, from 188Ta to 203Au, as 208Pb approached. Weisskopf hin-drance factors provide evidence for the erosion of the goodness of the K-quantum number, compatible with soft or axially symmetric shapes. The prolate-oblate phase transition region, with respect to tungsten, osmium and platinum, shows 195Os to be the pivotal nucleus in the osmium isotopic chain, with a calculated triaxial ground state. On comparison with the systematics of the region, results obtained for 190W show evidence for a Z = 74 sub-shell closure, analogous to that at Z = 64. Finally, new isotopes, 167Tb, 170Dy and 199Ir were discovered.
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Kobayashi, Fumiharu. "Systematic investigation of dineutron correlation in light neutron-rich nuclei." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188479.
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Patel, Zena. "K isomerism and collectivity in neutron-rich rare-earth isotopes." Thesis, University of Surrey, 2016. http://epubs.surrey.ac.uk/810640/.
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Neutron-rich rare-earth isotopes were produced by in-flight fission of 238U ions at the Radioactive Isotope Beam Factory (RIBF), RIKEN, Japan. In-flight fission of a heavy, high-intensity beam of 238U ions on a light target provides the cleanest secondary beams of neutron-rich nuclei in the rare-earth region of isotopes. In-flight fission is advantageous over other methods of nuclear production, as it allows for a secondary beam to be extracted, from which the beam species can be separated and identified. The excited states of nuclei are studied by delayed isomeric or beta-delayed gamma-ray spectroscopy. New K isomers were found in Sm (Z=62), Eu (Z=63), and Gd (Z=64) isotopes. The key results are discussed here. Excited states in the N~=~102 isotones 166Gd and 164Sm have been observed following isomeric decay for the first time. The K-isomeric states in 166Gd and 164Sm are due to 2-quasiparticle configurations. Based on the decay patterns and potential energy surface calculations, including beta6 deformation, both isomers are assigned a (6-) spin-parity. The half-lives of the isomeric states have been measured to be 950(60)ns and 600(140)ns for 166Gd and 164Sm respectively. Collective observables are discussed in light of the systematics of the region, giving insight into nuclear shape evolution. The decrease in the ground state band energies of 166Gd and 164Sm (N=102) compared to 164Gd and 162Sm (N=100) respectively, presents evidence for the predicted deformed shell closure at N=100. A 4-quasiparticle isomeric state has been discovered in 160Sm: the lightest deformed nucleus with a 4-quasiparticle isomer to date. The isomeric state is assigned an (11+) spin-parity with a measured half-life of 1.8(4)us. The (11+) isomeric state decays into a rotational band structure, based on a (6-) v5/2-[523] x v7/2+[633] bandhead, determined from the extracted gK-gR values. Potential energy surface and blocked BCS calculations were performed in the deformed midshell region around 160Sm. They reveal a significant influence from beta6 deformation and that 160Sm is the best candidate for the lightest four-quasiparticle K isomer to exist in this region. The relationship between reduced hindrance and isomer excitation energy for E1 transitions from multiquasiparticle states is considered with the new data from 160Sm. The E1 data are found to agree with the existing relationship for E2 transitions. K isomers were also observed in 159Sm, 161Sm, 162Sm, 163Eu, and 164Gd, some of them for the first time. Their level schemes are presented and discussed in terms of blocked BCS calculations. The reduced hindrance of E1 transitions in these isomers is discussed. Isomers are also observed in 164Eu, 165Eu, 167Tb, 168Tb, and 169Tb, however, the statistics are too low for analysis beyond gamma-ray energy measurements. The isotopes 160Sm, 161Sm, and 162Sm were populated for the first time via beta decay of 160Pm, 161Pm, and 162Pm respectively, also at the RIBF using in-flight fission. beta-delayed gamma rays are present in all three isotopes. Further analysis is needed to calculate the beta-decay half-lives.
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Albers, Michael [Verfasser]. "Evolution of nuclear deformation in neutron-rich Kr isotopes / Michael Albers." München : Verlag Dr. Hut, 2011. http://d-nb.info/1015606350/34.
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Hodsdon, Andrew. "The spectroscopy of neutron-rich phosphorus nuclei populated in grazing reactions." Thesis, University of the West of Scotland, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445721.
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Alkhomashi, Nasser. "Beta decay studies of heavy neutron-rich nuclei around A=190." Thesis, University of Surrey, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511112.
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Litzinger, Julia Maria [Verfasser]. "Nuclear structure studies of neutron-rich selenium isotopes / Julia Maria Litzinger." München : Verlag Dr. Hut, 2018. http://d-nb.info/1170474047/34.
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Barr, Matthew. "Alpha clustering in the ground state of neutron rich light nuclei." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4884/.
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An experiment was conducted at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, using the R³B experimental setup. This included an array of double sided silicon strip detectors and a 4π array of NaI scintillator detectors surrounding the target, a bending magnet and downstream fragment detectors consisting of scintillating fibre detectors and a plastic scintillator time of flight wall. Cross sections have been measured for the breakup of ^{7,9-12}Be and ^{8,10-15}B on proton and \(^↔\)C targets at beam energies between 260 and 540 MeV per nucleon. These cross sections have been analysed with a focus on comparison to cluster model theory. In the context of a large collaboration and an experiment with diverse physics objectives, it is worth clarifying the author's contribution to the work presented. The author participated in running the experiment, calibrated the Silicon Strip Detectors and performed all the analysis discussed in this thesis.
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Zanetti, Lorenzo [Verfasser], Thomas [Akademischer Betreuer] Aumann, and Joachim [Akademischer Betreuer] Enders. "Dipole excitations below the neutron separation threshold in neutron-rich Tin isotopes. / Lorenzo Zanetti ; Thomas Aumann, Joachim Enders." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/121823380X/34.
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Zanetti, Lorenzo Verfasser], Thomas [Akademischer Betreuer] [Aumann, and Joachim [Akademischer Betreuer] Enders. "Dipole excitations below the neutron separation threshold in neutron-rich Tin isotopes. / Lorenzo Zanetti ; Thomas Aumann, Joachim Enders." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/121823380X/34.
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Ollier, James. "The Yrast spectroscopy of neutron-rich nuclei produced in deep-inelastic processes." Thesis, University of the West of Scotland, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398328.
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Cullen, Ian J. "A study of neutron rich isomers and masses using a storage ring." Thesis, University of Surrey, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531377.
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Vadas, Jessica Elizabeth. "Probing the Fusion of Neutron-Rich Nuclei with Modern Radioactive Beam Facilities." Thesis, Indiana University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13423478.
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Fusion in neutron-rich environments is presently a topic of considerable interest. For example, the optical emission spectrum from the neutron star merger GRB170817A clearly establishes this neutron-rich environment as an important nucleosynthetic site. Fusion of neutron-rich light nuclei in the outer crust of an accreting neutron star has also been proposed as responsible for triggering X-ray super-bursts. The underlying hypothesis in this proposition is that the fusion of neutron-rich nuclei is enhanced as compared to stable nuclei. A good approach to understand how fusion proceeds in neutron-rich nuclei is to measure the fusion excitation function for an isotopic chain of nuclei. Modern radioactive beam facilities provide the opportunity to systematically address this question. An experimental program has been established to measure the fusion excitation function for light and mid-mass neutron-rich nuclei using low-intensity radioactive beams. The technique was initially demonstrated by measuring the fusion excitation functions for 18O and 19O nuclei incident on a 12C target. The beam of 19O ions was produced by the 18O(d,p) reaction with an intensity of 2-4 x 104 p/s at Florida State University. Evaporation residues resulting from the de-excitation of the fusion product were distinguished by measuring their energy and time-of-flight. To explore mid-mass neutron-rich nuclei much further from stability, the fusion excitation functions for 39,47K + 28Si were measured using the ReA3 reaccelerator facility at the National Superconducting Cyclotron Laboratory at Michigan State University. Incident ions were identified on a particle-by-particle basis by ΔE-TOF just upstream of the target. Fusion products were directly measured and identified by the E-TOF technique with an efficiency of ~70%. The measured fusion excitation functions for both the light and mid-mass systems have been compared to various theoretical models to elucidate how structure and dynamics impact the fusion of neutron-rich nuclei.
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Le, Bleis Tudi. "Experimental study of collective electric dipole mode in neutron-rich nickel nuclei." Strasbourg, 2009. http://www.theses.fr/2009STRA6252.
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Le travail présenté dans cette thèse a consisté pour une part à préparer des expériences sur les noyaux à asymétrie en isospin. En particulier, j’ai développé un nouveau système de lecture des modules VME pour le système d’acquisition des données associé à ces expériences. J’ai conservé autant que possible la modularité du système expérimental : l’ajout ou le retrait de modules doit rester simple autant que possible. Pour la seconde part, l’étude expérimentale d’une concentration de force dipolaire à basse énergie est présentée. Cette présentation inclue les outils théoriques utilisés, le mécanisme de réaction, le montage expérimental, la calibration des détecteurs et la détermination des sections efficaces. Ces dernières sont consistantes pour le 58Ni avec des mesures publiées obtenues en cinématiques directe. Une GDR seule ne peut expliquer les sections efficaces intégrales obtenues pour les émissions de neutrons à partir des noyaux de 67-69Ni. En particulier, ces sections efficaces sont consistantes avec une résonance pygmée localisée à 11MeV et représentant 8. 2(9)% de la règle de somme TRK pour le 68NiThe work of this thesis consisted on one hand, the preparation of experiments on isospin-asymmetric nuclei. In particular, I developed a new read-out for VME modules for the data acquisition system associated with those experiments. I developed this new read-out trying to keep the modularity of the experimental setup: adding and removing modules should be kept as easy as possible. On the other hand, an experiment on the low-lying dipolar strength is presented, from the theoretical tools involved to integrated cross-sections via the reaction mechanism, the experimental setup, the calibration of the detectors and the determination of the cross-section. In particular I found that the integral cross-section for 58Ni obtained by the Coulomb excitation is consistent with published results obtained by excitation in normal kinematics. The study of the dipolar response of 67-69Ni shows that the GDR cannot describe the measured cross sections. In particular the cross sections 68Ni are consistent with a pygmy resonance located at 11MeV and exhausting 8. 2(9)% of the TRK sum rule
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Gibelin, Julien. "Search for low lying dipole strength in the neutron rich nucleus 26Ne." Paris 11, 2005. http://www.theses.fr/2005PA112225.
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Nous avons effectué l'excitation Coulombienne, sur une cible de plomb, d'un faisceau exotique à 58 MeV/nucléon de 26Ne, noyau riche en neutrons, afin d'étudier la possible existence de résonances dipolaires pygmées au dessus du seuil d'émission neutron. L'expérience a été conduite auprès de l'accélérateur de l'institut RIKEN, à Tokyo (Japon) et incluait un détecteur de gammas, un hodoscope pour particules chargées et un détecteur de neutrons. A l'aide de la méthode de la masse invariante appliquée dans la voie de décroissance 25Ne+n, et en comparant la section efficace de réaction sur le plomb et sur une cible légère d'aluminium, nous observons de la force de moment angulaire égal à un entre les seuils d'émission un neutron et deux neutrons. A l'aide des distributions angulaire de diffusion du 26Ne nous en confirmons la nature et extrayons la valeur de probabilité de transition réduite dipolaire correspondante B(E1) = 0. 54 (0. 18) e2fm2. Notre méthode nous permet aussi d'accéder pour la première fois aux rapports d'embranchement de la décroissance d'une résonance pygmée. Par ailleurs, en détectant les photons de décroissance des états au-dessous du seuil d'émission neutron et en analysant les distributions angulaires de diffusion du 26Ne correspondant au premier état excité 2+, nous en déduisons sa probabilité de transition réduite, à partir de l'état fondamental. La valeur obtenue de B(E2) = 87 (13) e2fm4 est en désaccord avec le résultat d'une expérience précédenteWe carried out the Coulomb excitation, on a lead target, of an exotic beam of neutron-rich nucleus 26Ne at 58 A. MeV, in order to study the possible existence of a pygmy dipole resonance above the neutron emission threshold. The experiment was performed at the RIKEN Research Facility, in Tokyo (Japan) and included a gamma-ray detector, a charged fragment hodoscope and a neutron detector. Using the invariant mass method in the 25Ne+n decay channel, and by comparing the reaction cross section on the lead target and a light target of aluminium, we observe a sizeable amount of E1 strength between the one neutron and the two neutron emission thresholds. The corresponding 26Ne angular distribution confirms its nature and we deduce its reduced dipole transition probability value B(E1) = 0. 54 (0. 18) e2fm2. Our method also enables us to extract for the first time the decay pattern of a pygmy resonance. By detecting the decay photons from the excited states below the neutron emission threshold and by analyzing the angular distribution of the inelastically scattered 26Ne we deduce the reduced transition probability of the first 2+ state, from the ground state. The value obtained of B(E2) = 87 (13) e2fm4Being in disagreement with a previous result
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Lettmann, Marc. "Spectroscopy of neutron-rich germanium and krypton isotopes - A quest of triaxiality." Phd thesis, TUprints, 2018. https://tuprints.ulb.tu-darmstadt.de/7382/7/Dissertation_Lettmann_27_4_2018.pdf.
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This work covers the spectroscopic analysis of 84,86,88Ge and 94,96Kr isotopes populated by different reactions within the SEASTAR campaign 2015. The experimental setup and the data analysis are described in detail. This analysis includes necessary functionality checks and calibrations of the detectors along the beam line.
In-flight γ-ray spectroscopy of 84,86,88Ge was performed after various knock-out reactions. γ-spectroscopy of neutron-rich 88Ge was performed for the first time. The Doppler-corrected γ-ray spectra are analyzed with simulated lineshapes of occurring transitions. In total 16 transitions are observed ten of which so far unknown. New level schemes for 86,88 Ge are proposed based on the observed transition intensities and systematics of neighboring Ge isotopes.
The obtained level schemes are compared to state-of-the-art theoretical calculations. The assignment of a 3⁺ state of 86Ge agrees with new shell model and SCCM predictions. The agreement to the level orderings from the collective model by Davydov and co-workers points to an amount of rigid triaxiality in 86Ge. This is the first indication of rigid triaxiality in an unstable, neutron-rich nucleus.
In addition, an analysis of reaction cross sections, as well as cross sections for the excitation of a particular state is performed. This data set represents one of the first results for this newly-accessible region of the nuclear chart.
Furthermore, 84,86Ge and 94,96Kr are investigated after (p,p') reactions, which excite different states than the knock-out reactions. These states are candidates for octupole 3⁻ states, which are the first benchmark for the octupole degree of freedom in this exotic region. The obtained (p,p') cross sections of the 2⁺₁ states from 94,96Kr are compared to the transition strength known from literature based on the deformation length.
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Al-Garni, Sareh D. "Search for long lived isomers in the neutron-rich mass 180 region." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/843292/.
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Nuclei in the A~ 180 region were populated and investigated in a series of deep-inelastic reactions involving an 11.4 MeV per nucleon 136Xe beam produced by the GSI UNILAC accelerator, impinging on a selection of tantalum, tungsten and rhenium targets. The reaction products were released from both thermal (TIS) and FEBIAD ion sources and subsequently mass-separated using the GSI on-line mass separator. This work concentrates on the observation of gamma rays associated with the decay of the well known Kpi= 37/2--, t1/2 = 51.4 min. isomer in 177Hf. Due to the anomalous half-life characteristics and unexpectedly high yield of this decay, it is interpreted as being fed via the beta-decay of a high-K isomer in 177Lu. By comparing the experimental findings with the results obtained from multi-quasiparticle blocked-BCS-Nilsson calculations (which predict a low-lying state with Kpi = 39/2-- in 177Lu), the proposed decay is suggested to be an energetically favoured Kpi= 39/2-- five-quasiparticle state in 177Lu. A half-life of 7.7+/-3.0 min. is determined for this previously unreported A = 177 beta-decay path, also involving 89-keV and 1003-keV gamma-ray transitions in association with hafnium X-rays. In addition, two previously unreported transitions (2016 and 2114 keV) were assigned to 182Hf as a result of their coincidence with Hf X-rays and the 98 keV 2+ → 0+ decay of that nucleus.
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Steppenbeck, David. "Single-particle and collective excitations in neutron-rich sd- and fp-shell nuclei." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492748.
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Yrast and near-yrast structures in neutron-rich sd- and fp-shell nuclei have been deduced from four separate heavy-ion fusion-evaporation reactions performed at Argonne National Laboratory by exploiting different combinations of neutron-rich beams and targets.
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Wang, Zhimin. "γ-ray spectroscopy of neutron-rich silicon and sulphur nuclei using grazing reactions." Thesis, University of the West of Scotland, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.730021.
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Matoš, Milan. "Isochronous mass measurements of short-lived neutron rich nuclides at the FRS-ESR facilities." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972168656.
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Röder, Marko. "Measurement of the Coulomb dissociation cross sections of the neutron rich nitrogen isotopes 20,21N." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-157725.
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Many neutron rich nuclei are involved in the astrophysical r-process (rapid neutron capture process). The r-process forms an important path for heavy element nucleosynthesis and runs along the neutron drip line. Astrophysicists suggested core-collapse supernovae within a neutrino-driven wind scenario where the neutrino wind dissociates all previously formed elements into protons, neutrons and α particles, to be a possible astrophysical scenario for the r-process. Furthermore, reaction network calculations reported a high impact of light neutron rich nuclei to the r-process abundance. Reactions on these exotic nuclei can only be studied with radioactive ion beams as their half lifes, in the order of a few hundred milliseconds (T1/2,19N=330ms), are too low to fabricate target material out of them. Two examples of reactions along the path of the r-process are the 19N(n,γ)20N and the 20N(n, γ)21N reactions. Using 20N (resp. 21N) as a beam, these reactions were studied at the GSI Fragment Separator (FRS) in time-reversed conditions via Coulomb dissociation in the S393 experiment exploiting the virtual gamma field of a lead target. The experiment was performed at the LAND/R3B setup (Large Area Neutron Detector, Reactions with Relativistic Radioactive Beams) in a kinematically complete measurement, i.e., detecting all particles leaving the nuclear reaction. The neutrons flying at relativistic velocity were observed by the LAND detector, the calibration of which plays a crucial role for the present reaction. The Smiley effect, meaning that the measured energy of impinging particles in long scintillators is not independent of the hit position of the particle, has been investigated. It will be shown that reflections of the light traveling through the scintillator and the resulting longer path length of the light when not emitted directly towards the ends of the bar were identified to cause the Smiley effect. Gamma spectra in coincidence with outgoing 19N (resp. 20N) were generated. These fit well to recent publications and were utilized to separate transitions of the projectile nucleus into the ground state or first excited state of the ejectile nucleus. The Coulomb dissociation cross section was calculated for the total reaction, transitions into the ground state and the first excited state of the ejectile nucleus. Furthermore, excitation energy spectra were derived for both reactions separately for ground state transitions and for the dominating transitions into the first excited state. In order to facilitate future experiments on exotic nuclei, two detector solutions for the NeuLAND detector (the successor of LAND) were investigated. Utilizing minimum ionizing electrons of 30MeV at the ELBE facility, time resolutions and detection efficiencies were studied for an MRPC (Multi-gap Resistive Plate Chamber) based neutron detector with passive iron converters, on the one hand, and a pure scintillator based neutron ToF detector on the other hand. The ELBE data show good time resolutions (σt,electron < 120 ps) and detection efficiencies (ǫelectron > 90%) for both systems. Small MRPC prototypes were irradiated with 175MeV quasi-monochromatic neutrons at The Svedberg Laboratory (TSL) in Uppsala measuring efficiencies of ǫMRPC,neutron = 1.0%. It will be shown that MRPCs with passive steel converters may be included as neutron detectors in experiments where a lower multi-neutron capability than the one needed for NeuLAND is sufficientViele neutronenreiche Kerne sind im schnellen Neutroneneinfangprozess (r-Prozess, engl. für rapid) involviert. Der r-Prozess bildet einen wichtigen Pfad für die Nukleosynthese schwerer Elemente und verläuft entlang der Neutronen-Dripline. Astrophysiker schlugen Kernkollaps-Supernovae innerhalb eines neutrinogetriebenen Windes als mögliches astrophysikalisches Szenario für den r-Prozess vor. Dabei werden alle zuvor gebildeten Elemente in Protonen, Neutronen und Alphapartikel dissoziiert. Außerdem ist von Berechnungen mit Reaktionsnetzwerken bekannt, dass leichte neutronenreiche Kerne einen hohen Einfluss auf die Elementverteilung des r-Prozesses haben. Reaktionen dieser exotischen Kerne können nur mit radioaktiven Ionenstrahlen studiert werden, da ihre Halbwertszeiten im Bereich von wenigen hundert Millisekunden (T1/2,19N=330ms) zu gering sind, um Probenmaterial daraus herzustellen. Zwei Beispiele solcher Reaktionen, die auf dem Pfad des r-Prozesses liegen, sind die 19N(n,γ)20N und die 20N(n,γ)21N Reaktionen. Unter Verwendung von 20N (bzw. 21N) als Strahl wurden diese Reaktionen am Fragment Separator (FRS) der GSI unter zeitumgekehrten Bedingungen mittels Coulomb-Aufbruch gemessen, indem das virtuelle Photonenfeld einer Bleiprobe ausgenutzt wurde. Das Experiment wurde am LAND/R3B Aufbau (Large Area Neutron Detector, Reactions with Relativistic Radioactive Beams) in einer kinematisch vollständigen Messung durchgeführt, d.h. alle ausgehenden Reaktionsprodukte wurden detektiert. Die relativistischen Neutronen wurden mit dem LAND-Detektor untersucht. Dessen Kalibration spielt eine wichtige Rolle für die hier analysierten Reaktionen. Dabei wurde der Smiley-Effekt studiert, welcher beinhaltet, dass die gemessene Energie von einfallenden Teilchen mittels langen Szintillatorstreifen nicht unabhängig von der Position ist, an der die Teilchen auf den Detektor treffen. Es wird gezeigt, dass Reflexionen des Lichtes beim Durchgang durch den Szintillator und die größere Weglänge, die das Licht zurücklegen muss, wenn es nicht direkt in Richtung der Enden des Szintillators emittiert wird, den Smiley-Effekt verursachen. Gamma-Spektren in Koinzidenz mit ausgehenden 19N (bzw. 20N) wurden gewonnen und stimmen gut mit früheren Veröffentlichungen überein. Diese Spektren wurden dazu verwendet, die Übergänge des Projektilkerns in den Grundzustand und den ersten angeregten Zustand des Ejektilkerns zu identifizieren. Die Wirkungsquerschnitte des Coulombaufbruchs der Projektilkerne und die Anregungsenergiespektren beider Reaktionen wurden berechnet und separiert in Übergänge in den Grundzustand und die dominierenden Übergänge in den ersten angeregten Zustand. Um künftige Experimente an exotischen Kernen zu ermöglichen, wurden zusätzlich zwei Detektorkonzepte für NeuLAND (Nachfolger von LAND) untersucht. Mit minimal ionisierenden Elektronen mit Energien von 30MeV aus dem Elektronenbeschleuniger ELBE wurden die Zeitauflösungen und Detektionseffizienzen zum einen für einen MRPC (Multi-gap Resistive Plate Chamber) basierenden Neutronendetektor mit passiven Stahlkonverter und zum anderen für einen reinen szintillatorbasierenden Neutronendetektor studiert. Die ELBE-Daten zeigen gute Zeitauflösungen (σt,electron < 120ps) und Detektionseffizienzen (ǫelectron > 90%) für beide Systeme. Kleine MRPC-Prototypen wurden mit quasi-monochromatischen Neutronen mit einer Energie von 175MeV am TSL (The Svedberg Laboratory) in Uppsala bestrahlt. Dabei wurden Effizienzen von ǫMRPC,neutron = 1.0% gemessen. Es wird gezeigt, dass MRPCs mit passiven Stahlkonvertern als Neutronendetektoren bei Experimenten, bei denen eine geringere Multineutronenfähigkeit als für NeuLAND ausreichend ist, eingesetzt werden können
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Henrich, Corinna [Verfasser], Thorsten [Akademischer Betreuer] Kröll, and Wilfried [Akademischer Betreuer] Nörtershäuser. "Investigation of collectivity in the neutron-rich 142Xe / Corinna Henrich ; Thorsten Kröll, Wilfried Nörtershäuser." Darmstadt : Universitäts- und Landesbibliothek, 2021. http://d-nb.info/1226935451/34.
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Nakatsuka, Noritsugu. "Isoscalar and Isovector strengths of low-energy dipole excitations in neutron-rich unstable 20O." Kyoto University, 2018. http://hdl.handle.net/2433/232241.
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Mayet, Pascale. "Isomers populated by projectile fragmentation in the neutron-rich A=180-200 mass region." Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13131.
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Ansari, Saba. "Shape evolution in neutron-rich Zr, Mo and Ru isotopes around mass A=100." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS384/document.
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La forme d’un noyau, ou la déviation de la distribution en masse par rapport à une forme sphérique, est une des propriétés fondamentales du noyau. Elle est gouvernée à la fois par des effets macroscopiques et microscopiques, tels que l'énergie de liaison donnée par le modèle de la goutte liquide ou la structure en couche du noyau, respectivement. L’étude de la forme des noyaux exotiques par spectrométrie gamma permet de tester finement différents modèles théoriques initialement développés pour les noyaux stables. L’objectif de cette thèse est l’étude de l’évolution de la forme des noyaux exotiques riches en neutrons dans les chaînes isotopiques allant du Zr (Z=40) au Pd (Z=46). Le plus souvent, la forme des noyaux évolue lentement de la forme sphérique, près des fermetures de couche ou des noyaux magiques (ou doublement magiques), à des formes allongées (prolate), pour des noyaux avec de nombreux nucléons de valence. Cependant, Les noyaux auxquels nous nous intéressons ont tendance à avoir des états excités qui évoluent rapidement en fonction du nombre de neutrons, ce qui peut être interprété comme des variations rapides de la forme du noyau. Ceci inclue dans de rares cas l'observation d'états de forme aplatie (oblate) et triaxiale. Jusqu'à présent, les propriétés connues de ces noyaux se limitent (principalement) aux énergies d'excitation. Les informations sur le degré de collectivité nucléaire (que l'on peut déduire de la durée de vie des états excités) sont rares, tandis que les informations directes de forme sont pratiquement inexistantes. L'estimation la plus simple de la déformation nucléaire dans les noyaux pairs peut être obtenue à partir de l'énergie du premier état 2⁺. Pour les isotopes du Sr (Z = 38) et du Zr (Z = 40), il a été observé que cette énergie diminue considérablement à N = 60, alors que son évolution est beaucoup plus progressive pour les isotopes du Mo (Z = 42). Des mesures précises de durée de vie constituent un élément clé de l'étude systématique de l'évolution de la déformation nucléaire et du degré de collectivité dans cette région. Des noyaux riches en neutrons dans la région de masse A = 100-120 ont été peuplés par la réaction de fusion-fission d'un faisceau de ²³⁸U à 6,2 MeV/u sur une cible ⁹Be. Le noyau composé ²⁴⁷Cm était produit à une énergie d'excitation de ∼45 MeV avant de fissionner. Le dispositif expérimental utilisé pour cette étude comprenait le spectromètre de masse de haute résolution VAMOS pour l'identification les noyaux en Z et A, le réseau de 35 détecteurs au germanium AGATA (Advanced γ-ray Tracking Array) AGATA, pour la spectroscopie de rayons γ, ainsi qu'un mécanisme de "plunger" pour mesurer la durée de vie jusqu'à quelques ps par la méthode RDDS (Recoil Distance Doppler Shift). De plus, la cible était entourée de 24 détecteurs LaBr₃ (Bromure de lanthane) pour mesurer des durées de vie plus de 100 ps avec la méthode du "fast-timing". La combinaison de spectromètres sophistiqués utilisée dans cette expérience a permis de mesurer des durées de vie d'états nucléaires allant de 100 picosecondes à quelques picosecondes. Dans cette thèse, nous exposerons de nouveaux résultats pour les états à courte durée de vie dans les noyaux riches en neutrons A∼100, en mettant l'accent sur les chaînes des Zr, Mo et Ru. Nous discuterons des techniques expérimentales utilisées pour évaluer les durées de vie ainsi que l'interprétation de celles-ci à l'aide de modèles de structures nucléaires récentsThe shape of an atomic nucleus, ie. the deviation of its mass distribution from sphericity, is a fundamental property and governed by a delicate interplay of macroscopic and microscopic effects, such as the liquid-drop like binding energy and the nuclear shell structure, respectively. Studying nuclear shape properties using gamma ray spectroscopic methods allows detailed tests of different nuclear models, which were originally developed for stable nuclei. We proposed a project to study the evolution of nuclear shapes in exotic nuclei, far from the valley of stability, specifically in neutron-rich nuclei in the isotopic chains from Zr (Z=40) to Pd (Z=46). Usually, nuclear shapes are slowly evolving from spherical shapes around closed-shell or (doubly-) magic nuclei to elongated (prolate) shapes in nuclei with many valence nucleons. The nuclei of interest, however, show rapidly evolving patterns of excited states, which can be interpreted as rapid variations of the nuclear shape, including the rare observation of oblate (disk-like) and triaxial shapes. So far the known properties for these nuclei are (mainly) limited to excitation energies. Information on the nuclear collectivity, which can be deduced from the lifetime of the excited states, are sparse, while direct information of the shape is practically non existing. The simplest estimate of nuclear deformation in even-even nuclei can be obtained from the energy of the first 2⁺ state. For Sr (Z = 38) and Zr (Z = 40) isotopes this energy is observed to decrease dramatically at N = 60, while its evolution is much more gradual in Mo nuclei (Z = 42). Precise lifetime measurements provide a key ingredient in the systematic study of the evolution of nuclear deformation and the degree of collectivity in this region. Neutron-rich nuclei in the mass region of A = 100-120 were populated through the fusion-fission reaction of a ²³⁸U beam at 6.2 MeV/u on a ⁹Be target. The compound nucleus ²⁴⁷Cm was produced at an excitation energy of around 45 MeV before undergoing fission. The setup used for this study comprised the high-resolution mass spectrometer VAMOS in order to identify the nuclei in Z and A, the Advanced gamma ray Tracking Array AGATA of 35 germanium detectors to perform gamma ray spectroscopy, as well as a plunger mechanism to measure lifetimes down to a few ps using the Recoil Distance Doppler Shift method (RDDS). In addition, the target was surrounded by 24 Lanthanum Bromide (LaBr₃) detectors for a fast-timing measurement of lifetimes longer than 100 ps. The sophisticated set of spectrometers used in this experiment allowed measurement of nuclear lifetimes in a range from 100’s of picoseconds down to a few picoseconds. In this thesis, we will report on new lifetime results for short-lived states in neutron-rich (A ~ 100) nuclei, with an emphasis on the Zr, Mo and Ru chains. We will discuss the experimental techniques used to evaluate the lifetimes as well as their interpretation in terms of state-of-the-art nuclear structure models
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Seidlitz, Michael [Verfasser]. "Nuclear shell effects in neutron-rich nuclei around N = 20 and N = 32,34 / Michael Seidlitz." München : Verlag Dr. Hut, 2013. http://d-nb.info/1045987697/34.
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Al-Dahan, Nawras M. S. "Isomer and (beta)-delayed gamma-ray spectroscopy for structure studies of heavy, neutron-rich nuclei." Thesis, University of Surrey, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520560.
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Mougeot, Maxime. "Nuclear Collectivity Studied through High Precision Mass Measurements of Neutron-rich Argon and Chromium Isotopes." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS455/document.
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Le lien étroit existant entre la masse d'un noyau et son énergie de liaison fait de la masse un observable incontournable pour enrichir notre compréhension de l'évolution de la structure nucléaire dans des régions de la carte des noyaux éloignées de la vallée de la stabilité. Dans cette thèse deux régions présentant d'importants changements structurales sont étudiés à travers des mesures de masses de haute précision effectuées à ISOLDE/CERN avec le spectromètre ISOLTRAP. De nombreux résultats de spectroscopie nucléaire indiquent que la chaîne isotopique du chrome présente les changements structurales les plus importants dans toute la région de déformation nucléaire observée au sud du nickel 68. Cette thèse présente les premières mesures de haute précision des isotopes 58-63Cr grâce à des techniques de spectrométrie de masse de pointe faisant appel à l'utilisation d'un piège de Penning ainsi qu'à un spectromètre en temps de vol de type MRToF-MS. Les mesures ainsi obtenues sont jusqu'à 300 fois plus précises que celles disponibles dans la littérature actuelle. Au contraire des résultats précédents, ces nouvelles mesures suggèrent une évolution progressive de l'état fondamental des chromes vers la déformation aux abords de N=40. La question de la persistance de la fermeture de couche à N=28 dans la chaine de l'argon est aussi abordée dans le cadre de cette thèse de doctorat à travers la mesure des isotopes 46-48 de l'argon. Les résultats d'une précision améliorée confirment la présence d'une forte fermeture de couche à N=28 dans l'argon. Pour chaque jeu de données la procédure d'analyse est détaillée. L'implication pour la physique nucléaire des résultats expérimentaux obtenus sont discutés de manière phénoménologique ainsi qu'à travers des modèles représentant l'état de l'art de la recherche en physique nucléaire théoriqueDue to their inherent relationship with the binding energy, nuclear masses are the fingerprint of all the interactions taking place within the nucleus. As such, precise and accurate mass values are an essential ingredient to the comprehensive understanding of nuclear phenomena in exotic regions of the chart of nuclides. In this thesis, two key regions exhibiting dramatic structural evolution are investigated by means of high precision mass measurements performed with the online mass spectrometer ISOLTRAP at ISOLDE/CERN. Numerous spectroscopy results indicate that the chromium isotopic chain exhibits the most dramatic structural changes within the region situated south of 68Ni. This thesis reports on the first high-precision mass measurements of the neutron-rich 58-63Cr isotopes using the well established Penning trap mass spectrometry technique as well as the MRToF-MS technique pioneered at ISOLTRAP in recent years. The obtained mass values are up to 300 times more precise than the ones currently available in the literature. At odds with previous results, the new mass values exclude a sudden onset of ground-state collectivity rather favouring a smooth transition towards deformation approaching N=40. The question of the persistence of the N=28 shell closure in the Argon chain is also studied in this PhD work through the measurement of the neutron-rich 46-48Ar isotopes. The results of improved precision confirm the presence of a strong N=28 shell closure in the Argon chain. For both datasets, the detailed data analysis procedure will be presented. The implication of the obtained mass values for nuclear structure will be discussed through a phenomenological discussion of the binding energy trend. The results will also be discussed in the light of state of the art nuclear models including results from the promising valence-space formulation of the ab-initio IM-SRG formalism
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Sugimura, Hitoshi. "Search for 6ΛH hypernucleus by the (π-,K+) reaction at J-PARC." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188482.
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Söderström, Pär-Anders. "Collective Structure of Neutron-Rich Rare-Earth Nuclei and Development of Instrumentation for Gamma-Ray Spectroscopy." Doctoral thesis, Uppsala universitet, Kärnfysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-149772.
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Neutron-rich rare-earth nuclei are among the most collective nuclei that can be found in nature. In particular, the doubly mid-shell nucleus 170Dy is expected to be the nucleus where the collective structure is maximized. This has implications for the astrophysical r-process, since it has been suggested that the collectivity maximum plays an important role in the abundances of the rare-earth elements that are created in supernova explosions. In this work, the collective structure of the five nuclei 168,170Dy and 167,168,169Ho are studied and different theoretical models are used to interpret the evolution of collectivity around the mid-shell. In order to produce and study even more neutron-rich nuclei in this mass region, new radioactive ion beam facilities will be a valuable tool. These facilities, however, require advanced instruments to study the weak signals of exotic nuclei in a high background environment. Two of these instruments are the γ-ray tracking spectrometer AGATA and the neutron detector array NEDA. For AGATA to work satisfactorily, the interaction position of the gamma rays must be determined with an accuracy of at least five millimetres. The position resolution is measured in this work using a model independent method based on the Doppler correction capabilities of the detector at two different distances between the detector and the source. For NEDA, one of the critical parameters is its ability to discriminate between neutrons and γ rays. By using digital electronics it is possible to employ advanced and efficient algorithms for pulse-shape discrimination. In this work, digital versions of the common analogue methods are shownto give as good, or better, results compared to the ones obtained using analogue electronics. Another method which effectively distinguishes between neutrons and γ rays is based on artificial neural networks. This method is also investigated in this work and is shown to yield even better results.
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Iafigliola, Rocco. "Beta decay energies and strength function of neutron rich isotopes in the A = 91-100 region." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70358.
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A solid-state DE-E telescope beta spectrometer has been built and used to study beta-minus spectra. The system consists of a 15 mm x 500 mm$ sp2$ hyperpure germanium (HPGe) E-detector and a 300 $ mu$m x 200 mm$ sp2$ Si DE-detector with a special "keyhole" design.The response function of the system has been determined experimentally using mono-energetic electron beams with incident energies ranging from 1 to 12 MeV.
The beta endpoint energies of 25 nuclei, namely, $ sp{32}$P, $ sp{88}$Rb, $ sp{91-99}$Rb, $ sp{91-96}$Sr, $ sp{99-100}$Sr, $ sp{92-96}$Y and $ sp{100}$Y have been measured. The Q-beta values and mass excesses for A = 91-100 have been determined. The results for $ sp{99}$Rb, $ sp{99-100}$Sr and $ sp{100}$Y have been obtained for the first time.
The beta strength functions for odd mass Rb isotopes, namely $ sp{91-99}$Rb have been measured for the first time from direct beta spectroscopy with a solid-state telescope system. The experimental results have been compared to calculations using the Brown-Bolsterli (B-B) model.
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Syndikus, Ina Josephine [Verfasser], Marina [Akademischer Betreuer] Petri, and Thomas [Akademischer Betreuer] Aumann. "Proton-Knockout Reactions from Neutron-Rich N Isotopes at R3B / Ina Josephine Syndikus ; Marina Petri, Thomas Aumann." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1194547737/34.
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Morfouace, Pierre. "Single-particle states in neutron-rich 69Cu and 71Cu by means of the (d,3He) transfer reaction." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112196/document.
Full textAbstract:
A l'aide de deux réactions de transfert (d,3He), la première avec MUST2 au GANIL et la deuxième avec le split-pole à Orsay, nous avons déterminé la position des états trous de protons dans les noyaux riches en neutrons : le 71Cu (N=42) et le 69Cu (N=40).A partir de la désintégration beta et de la spectroscopie laser, on sait que l'état excité f5/2 chute brutalement en énergie pour N>40 et devient même l'état fondamental dans le 75Cu. Cette chute en énergie a été expliqué par des travaux théoriques notamment à cause de la force tenseur entre les protons et les neutrons. La prédiction sur le partenaire spin-orbite f7/2 est qu'il devrait sentir également un effet à cause de cette force. Expérimentalement, les états trous de proton f7/2 ne sont pas connus pour N>40. Dans le 71Cu, deux états 7/2- sont connus autour de 1 MeV d'énergie d'excitation et sont des possibles candidats pour correspondre à cet état trou de proton. L'expérience au GANIL a eu lieu en mars 2011. Un faisceau secondaire de 72Zn à 38 AMeV a été produit par fragmentation et purifié à travers le spectromètre LISE. La réaction de transfert en cinématique inverse a été étudié à l'aide des télescopes MUST2 plus quatre détecteurs de silicium de 20 micromètres dans le but d'identifier les 3He de basse énergie. Le spectre en énergie d'excitation du 71Cu a été reconstruit grâce à la méthode de la masse manquante, les distributions angulaires ont été extraite et comparé avec un modèle de réaction utilisant les codes DWUCK4 et DWUCK5. A partir de ce travail au GANIL, aucun état n'a été peuplé autour de 1 MeV concluant que le centroid de la force réside à plus haute énergie d'excitation.Nous avalons également mesuré une nouvelle fois la les états trous de proton dans le 69Cu avec la même réaction de transfert mais cette fois en cinématique directe à Orsay dans le but d'étendre les données actuelles sur ce noyau où 60% de la force f7/2 est manquante et dans le but également d'avoir une analyse consistante des facteurs spectroscopiques entre les deux noyaux. Cette analyse consistante nous permet de pouvoir comparer l'évolution du centroid de la force entre les deux isotopes quand l'orbite neutron g9/2 commence à se remplir. Dans cette seconde expérience, nous avons utilisé un faisceau de deuton à 27 MeV produit par le tandem et une cible de 70Zn. Nous avons pu extraire trois nouvelles distributions angulaires et mesurer une nouvelle partie de la force f7/2.Enfin, pour pouvoir interpréter nos résultat, des calculs modèle en couche ont été effectué par le groupe de Strasbourg avec le code Antoine. L'espace de valence utilisé consiste en un coeur 48Ca avec les orbitales protons f7/2, p3/2, f5/2, p1/2 et les orbitales neutron p3/2, f5/2, p1/2, g9/2, d5/2. Les calculs inclus jusqu'à 8p-8h et montrent que la force se situe en effet à haute énergie d'excitation et qu'aucun état de trou de proton n'est calculé autour de 1 MeVIn two (d,3He) transfer reactions with MUST2 at GANIL and the split-pole at Orsay, we have determined the position of the proton-hole states in the neutron-rich 71Cu (N=42) and 69Cu (N=40) isotopes. We have found that in 71Cu the hole strength of the f7/2 orbital lies at higher excitation energies than expected. From beta-decay and laser spectroscopy, the f5/2 first excited particle state in these isotopes was known to come down rapidly in energy when passing N=40 and even become the ground state in 75Cu. This sudden energy shift has been explained in a number of theoretical works. The prediction for the f7/2 spin-orbit partner was that it would change in energy too through a related effect. Experimentally, the f7/2 proton-hole state is not known for N>40. In 71Cu two 7/2- states around 1 MeV are candidates to be a proton-hole.The experiment at GANIL took place in March 2011. A secondary beam of 72Zn at 38 AMeV was produced by fragmentation and purified through the LISE spectrometer. The transfer reaction in inverse kinematics was studied with the MUST2 detectors plus four 20 micrometer silicon detector to identified the 3He of low kinetic energy. The excitation spectrum of 71Cu was reconstruct thanks to the missing mass method and the angular distributions were extracted and compared with a reaction model using the DWUCK4 and DWUCK5 code. From this work no states have been populated around 1 MeV concluding that the centroid of the f7/2 lies at higher excitation energy. We then remeasured the single-particle strength in 69Cu in the corresponding (d,3He) reaction at Orsay in March 2013 in order to extend the existing data where 60% of the f7/2 strength is missing and make sure that there is a consistent analysis of spectroscopic factors between both isotopes in order to well understood and well quantify the evolution of the f7/2 orbital when we start filling the g9/2 orbital. In this second experiment we have performed the reaction in direct kinematics using a deuteron beam at 27 MeV provided by the tandem and a target of 70Zn. In this work we were able to extract three new angular distributions and we have measured a new part of the f7/2 strength.Finally in order to interpret the results we have obtained from those two experiments, state-of-the-art shell-model calculations have been carried out in collaboration with the Strasbourg group using the Antoine code. The valence space consists in a core of 48Ca with the valence orbitals for protons f7/2, p3/2, f5/2, p1/2 and the orbitals p3/2, f5/2, p1/2, g9/2, d5/2 for neutrons. The calculations have been done allowing 8p-8h and show that the strength is indeed at high energy and no f7/2 proton-hole state lies around 1 MeV in 71Cu
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Browne, Frank. "Deformed structures in neutron-rich A ≈ 100 nuclei studied by isomer and ß- delayed γ-ray spectroscopy." Thesis, University of Brighton, 2016. https://research.brighton.ac.uk/en/studentTheses/fc8d1987-8244-4320-8673-a1973c508f95.
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Neutron-rich A∼110 nuclei have been the subject of intensive discussion since the discovery of a rapid onset of ground-state static quadrupole deformation in the A > 100 Zr nuclei over 60 years ago. The results presented in this thesis further the experimental knowledge of such deformations towards more exotic isotopes in this region. An experiment was carried out at the Radioactive Isotope Beam Factory, RIKEN, Wako-shi, Japan. Nuclei of interest were produced through the in-flight abrasion fission of a 345 MeV/nucleon 238U beam by a 555 mg/cm2 9Be target and selected by the BigRIPS spectrometer according to their mass-to-charge ratio and atomic charge. They were implanted into the WAS3ABi silicon stack and γ rays emitted following β-decay, or decay of isomeric states were detected in an array of 12 cluster HPGe (EURICA) and 18 LaBr3(Ce) detectors. A newly implemented fast β-γ timing configuration provided access to the lifetimes of excited states in the nanosecond regime. In particular, the lifetime of the 2+ state of 106Zr is reported for the first time, as well as a more precise measurement for 104Zr, compared to the adopted value. These measurements, combined with the energy of the ground-state transition, have been used to deduce the reduced transition probability and from this a model-dependent value for the ground-state deformation. New isomeric states have also been observed in 102Zr, 113Nb and 115Mo. The reduced transition probability of the 2+ + g.s transition in 106Zr shows a marked decrease from that of 104Zr. This reflects the energy systematics, and further confirms the deformed sub-shell closure at N=64. Comparisons of the systematics of the observed reduced transition probabilities to those calculated in the IBM-1 model show poor agreement. However, calculations based on the nuclear-shell model in a deformed basis state, show good agreement with observation, demonstrating the reliability of the employed ground-state wavefunction. The isomeric state in 102Zr is ascribed to a change in the K quantum number, and the isomeric states in 113Nb and 115Mo are proposed to be due to shape stabilisation of excited states.
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Syndikus, Ina [Verfasser], Marina [Akademischer Betreuer] Petri, and Thomas [Akademischer Betreuer] Aumann. "Proton-Knockout Reactions from Neutron-Rich N Isotopes at R3B / Ina Josephine Syndikus ; Marina Petri, Thomas Aumann." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1194547737/34.
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Yoshida, Kenichi. "Pair correlation and continuum coupling effects on low-frequency modes of excitation in deformed neutron-rich nuclei." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136769.
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Steiger, Konrad [Verfasser], Reiner [Akademischer Betreuer] Krücken, and Peter [Akademischer Betreuer] Fierlinger. "Decay spectroscopy of neutron-rich nuclei around 37Al / Konrad Steiger. Gutachter: Peter Fierlinger ; Reiner Krücken. Betreuer: Reiner Krücken." München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1034134752/34.
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