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Journal articles on the topic 'Positron annihilation'

Author: Grafiati

Published: 4 June 2021

Last updated: 30 July 2024

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1

Lingenfelter, Richard E., and Reuven Ramaty. "Annihilation Radiation and Gamma-Ray Continuum from the Galactic Center Region." Symposium - International Astronomical Union 136 (1989): 587–605. http://dx.doi.org/10.1017/s0074180900187091.

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Observations of the time-dependent, electron-positron annihilation line radiation and gamma-ray continuum emission from the region of the Galactic Center show that there are two components to the annihilation line emission: a variable, compact source at or near the Galactic Center, and a steady, diffuse interstellar distribution. We suggest that the annihilating positrons in the compact source, observed from 1977 through 1979, result from photon-photon pair production, most likely around an accreting black hole, and that the annihilating, interstellar positrons result from the decay of radionuclei produced by thermonuclear burning in supernovae.

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2

Lynn, K. G., Bent Nielsen, and D. O. Welch. "Hydrogen interaction with oxidized Si(111) probed with positrons." Canadian Journal of Physics 67, no. 8 (August 1, 1989): 818–20. http://dx.doi.org/10.1139/p89-141.

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A variable-energy positron beam was utilized to study the interface action of hydrogen with Si(111) covered by an ultrahigh-vacuum thermally grown oxide of 2–3 nm thickness. It was observed that positrons implanted at shallow depth (<100 nm) after diffusion are trapped either at the interface between the oxide and the Si or in the oxide. The positron-annihilation characteristics of these trapped positrons are found to be very sensitive to hydrogen exposure. The momentum distribution of the annihilating positron–electron pair, as observed in the Doppler broadening of the annihilation line, broadens considerably after exposure to hydrogen. The effect recovers after annealing at [Formula: see text], suggesting a hydrogen binding at the interface of ~3 ± 0.3 eV.

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3

Stewart, A. T., C. V. Briscoe, and J. J. Steinbacher. "Positron annihilation in simple condensed gases." Canadian Journal of Physics 68, no. 12 (December 1, 1990): 1362–76. http://dx.doi.org/10.1139/p90-196.

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The angular-correlation technique of positron annihilation has been used to detect and measure the localized bubble state of positronium (Ps) in liquid Ne, Ar, Kr, H2, and N2 and in liquid and solid He at various pressures and temperatures. No bubble state was seen in liquid O2 or in solid Ne and Ar. The dynamics of bubble formation is not yet understood. In the cases where theoretical calculations, and adequate data, exist, viz. He, Ar, and H2, there is reasonable agreement for the momentum of the photons from the annihilation of positrons with the outer electrons of these atoms. The Ps annihilations from the self-trapped bubble state are reasonably well described in terms of a simple finite potential-well model.

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4

Panther, Fiona H., Roland M. Crocker, Ivo R. Seitenzahl, and Ashley J. Ruiter. "SN1991bg-like supernovae are a compelling source of most Galactic antimatter." Proceedings of the International Astronomical Union 11, S322 (July 2016): 176–79. http://dx.doi.org/10.1017/s1743921316011911.

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AbstractThe Milky Way Galaxy glows with the soft gamma ray emission resulting from the annihilation of ~5 × 1043 electron-positron pairs every second. The origin of this vast quantity of antimatter and the peculiar morphology of the 511keV gamma ray line resulting from this annihilation have been the subject of debate for almost half a century. Most obvious positron sources are associated with star forming regions and cannot explain the rate of positron annihilation in the Galactic bulge, which last saw star formation some 10 Gyr ago, or else violate stringent constraints on the positron injection energy. Radioactive decay of elements formed in core collapse supernovae (CCSNe) and normal Type Ia supernovae (SNe Ia) could supply positrons matching the injection energy constraints but the distribution of such potential sources does not replicate the required morphology. We show that a single class of peculiar thermonuclear supernova - SN1991bg-like supernovae (SNe 91bg) - can supply the number and distribution of positrons we see annihilating in the Galaxy through the decay of 44Ti synthesised in these events. Such 44Ti production simultaneously addresses the observed abundance of 44Ca, the 44Ti decay product, in solar system material.

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5

Wagner, A., M. Butterling, F. Fiedler, F. Fritz, M. Kempe, and T. E. Cowan. "Position-resolved Positron Annihilation Lifetime Spectroscopy." Journal of Physics: Conference Series 443 (June 10, 2013): 012091. http://dx.doi.org/10.1088/1742-6596/443/1/012091.

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6

Gajos, Aleksander. "Sensitivity of Discrete Symmetry Tests in the Positronium System with the J-PET Detector." Symmetry 12, no. 8 (August 1, 2020): 1268. http://dx.doi.org/10.3390/sym12081268.

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Study of certain angular correlations in the three-photon annihilations of the triplet state of positronium, the electron–positron bound state, may be used as a probe of potential CP and CPT-violating effects in the leptonic sector. We present the perspectives of CP and CPT tests using this process recorded with a novel detection system for photons in the positron annihilation energy range, the Jagiellonian Positron Emission Tomography (J-PET). We demonstrate the capability of this system to register three-photon annihilations with an unprecedented range of kinematical configurations and to measure the CPT-odd correlation between positronium spin and annihilation plane orientation with a precision improved by at least an order of magnitude with respect to present results. We also discuss the means to control and reduce detector asymmetries in order to allow J-PET to set the first measurement of the correlation between positronium spin and momentum of the most energetic annihilation photon which has never been studied to date.

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7

Jean, Y. C., X. Lu, Y. Lou, A. Bharathi, C. S. Sundar, Y. Lyu, P. H. Hor, and C. W. Chu. "Positron annihilation inC60." Physical Review B 45, no. 20 (May 15, 1992): 12126–29. http://dx.doi.org/10.1103/physrevb.45.12126.

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8

OUGIZAWA, Toshiaki. "Positron Annihilation Spectroscopy." Kobunshi 55, no. 9 (2006): 750–54. http://dx.doi.org/10.1295/kobunshi.55.750.

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9

OUGIZAWA, Toshiaki, and Makoto MURAMATSU. "Positron Annihilation SPectroscoPy." Kobunshi 51, no. 10 (2002): 831. http://dx.doi.org/10.1295/kobunshi.51.831.

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10

Belyanin, A. A., V. V. Kocharovskii, and Vl V. Kocharovskii. "Collective Electron-Positron Annihilation." International Astronomical Union Colloquium 128 (1992): 117–22. http://dx.doi.org/10.1017/s0002731600154903.

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AbstractThe phenomenon of collective spontaneous annihilation of a magnetized electron-positron plasma is predicted. Like the superradiance in systems with discrete energy spectra, collective annihilation leads to the generation of powerful coherent radiation with the rate of this process considerably exceeding the spontaneous annihilation and collisional relaxation rates.

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11

Seeger, Alfred, Andreas Siegle, and Hermann Stoll. "Positron Annihilation in Stable and Supercooled Metallic Melts." International Journal of Materials Research 92, no. 7 (July 1, 2001): 632–44. http://dx.doi.org/10.1515/ijmr-2001-0124.

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Abstract The stable and supercooled melts as well as the crystalline phases of Ga, In, Sn, Pb, and Bi have been investigated in the age –momentum correlation (AMOC) positron annihilation facility at the Stuttgart pelletron. The comparison of the lineshape parameter S, characterizing the momentum distribution of the annihilating electron –positron pairs, and of the mean positron lifetime with measurements of the positron diffusivity confirms in considerable detail the ‘polaron’ model of positrons in metallic melts developed earlier. The quantitative analysis of the data provides us with valuable information on the structure of the melts. E. g., in the investigated melts the existence of an appreciable concentration of ‘free volumes’ comparable in size with the atomic volume can be excluded. It is shown that this is in accord with earlier deductions from self-diffusivity measurements. An interesting but hitherto incompletely understood correlation between the entropy of fusion and the absence of trapping of positrons by vacancies in thermal equilibrium is pointed out.

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12

Kobayashi, Yoshinori. "Positron Chemistry in Polymers." Defect and Diffusion Forum 331 (September 2012): 253–74. http://dx.doi.org/10.4028/www.scientific.net/ddf.331.253.

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Positron chemistry refers to chemical processes of high-energy positrons injected into molecular substances, the most interesting of which is the formation of positronium (Ps), the hydrogen-like bound state between a positron and an electron. Ps is formed predominantly by fast intra-track radiation chemical processes. In polymers it tends to be localized in intra/inter-molecular open space in the sparsely packed amorphous structure. Whilst short-lived singletpara-positronium (p-Ps) undergoes self-annihilation, the positron in long-lived tripletortho-positronium (o-Ps) annihilates with one of the spin opposite electrons bound in the surrounding polymer molecules. This process is called pick-off annihilation. The pick-off annihilation lifetime reflects the polymer chain packing through the size of the volume, where Ps is localized. Positrons are used to probe the amorphous structure of various polymeric systems. In this article, basic concepts and experimental techniques of positron chemistry in polymers as well as applications to the characterization of functional polymeric materials are overviewed.

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13

Lawther, D. W., and R. A. Dunlap. "Positron Annihilation in Quasicrystals." Materials Science Forum 175-178 (November 1994): 431–34. http://dx.doi.org/10.4028/www.scientific.net/msf.175-178.431.

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14

Jean, Yan Ching. "Positron Annihilation in Polymers." Materials Science Forum 175-178 (November 1994): 59–70. http://dx.doi.org/10.4028/www.scientific.net/msf.175-178.59.

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15

Shiryaev, A. A., K. Iakoubovskii, H. Schut, A. van Veen, R. Escobar Galindo, O. D. Zakharchenko, Yu A. Klyuev, F. Kaminsky, and B. N. Feigelson. "Positron Annihilation in Diamond." Materials Science Forum 363-365 (April 2001): 40–46. http://dx.doi.org/10.4028/www.scientific.net/msf.363-365.40.

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16

Peter, M., Thomas Jarlborg, B. Barbiellini, Alfred A. Manuel, L. Hoffmann, Arun Shukla, E. Walker, P. Lerch, and W. Sadowski. "Positron Annihilation in YBaCuO." Materials Science Forum 105-110 (January 1992): 411–18. http://dx.doi.org/10.4028/www.scientific.net/msf.105-110.411.

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17

Enoto, Teruaki. "Positron Annihilation in Thunderstorms." Nuclear Physics News 29, no. 3 (July 3, 2019): 22–27. http://dx.doi.org/10.1080/10619127.2019.1642716.

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18

Tuomisaari, M., K. Rytsola, and P. Hautojarvi. "Positron annihilation in xenon." Journal of Physics B: Atomic, Molecular and Optical Physics 21, no. 23 (December 14, 1988): 3917–28. http://dx.doi.org/10.1088/0953-4075/21/23/011.

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19

Hutchins, Stephen, Paul Beasley, and Christine Bull. "Particle Spectroscopy: Positron annihilation." Physics Bulletin 36, no. 5 (May 1985): 199–200. http://dx.doi.org/10.1088/0031-9112/36/5/018.

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20

Ito, Yutaka, Yoshihiro Iwasa, Nguen Mahn Tuan, and Shin-ichi Moriyama. "Positron annihilation inside C60." Journal of Chemical Physics 115, no. 10 (September 8, 2001): 4787–90. http://dx.doi.org/10.1063/1.1386805.

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21

Kurfess, J. D. "Galactic positron annihilation radiation." Advances in Space Research 25, no. 3-4 (January 2000): 631–40. http://dx.doi.org/10.1016/s0273-1177(99)00815-7.

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22

Leguey, T., M. A. Monge, R. Pareja, and J. M. Riveiro. "Positron annihilation in samarium." Journal of Physics: Condensed Matter 7, no. 30 (July 24, 1995): 6179–85. http://dx.doi.org/10.1088/0953-8984/7/30/019.

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23

Nicolau, Y. F., and P. Moser. "Positron annihilation in polyaniline." Synthetic Metals 47, no. 1 (April 1992): 9–20. http://dx.doi.org/10.1016/0379-6779(92)90329-h.

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24

Peter, M., L. Hoffmann, and A. A. Manuel. "Positron annihilation and superconductivity." Physica C: Superconductivity 153-155 (June 1988): 1724–27. http://dx.doi.org/10.1016/0921-4534(88)90461-3.

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25

Ito, Y. "Applications of positron annihilation." International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes 37, no. 1 (January 1986): 82–83. http://dx.doi.org/10.1016/0883-2889(86)90219-4.

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26

Sundararajan, V., and D. G. Kanhere. "Positron annihilation in copper." Pramana 34, no. 1 (January 1990): 33–49. http://dx.doi.org/10.1007/bf02846107.

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27

AMRANE, N. "POSITRON ANNIHILATION IN SiC." International Journal of Modern Physics C 13, no. 07 (September 2002): 957–66. http://dx.doi.org/10.1142/s0129183102003711.

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Valence electron and positron charge densities in SiC are obtained from wave functions derived in a model pseudopotential bandstructure calculation. It is observed that the positron density is maximum in the open interstices and is excluded not only from the ion cores but also, to a considerable degree, from the valence bonds. Electron–positron momentum densities are calculated for the (001–110) plane. The results are used to analyze the positron effect in large gap semiconductors.

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28

Chojcan, J., and M. Sachanbiński. "Positron Annihilation in Obsidians." Acta Physica Polonica A 88, no. 1 (July 1995): 103–10. http://dx.doi.org/10.12693/aphyspola.88.103.

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29

RAMATY, R., and R. E. LINGENFELTER. "Galactic Positron Annihilation Radiation." Annals of the New York Academy of Sciences 655, no. 1 Frontiers in (June 1992): 319–25. http://dx.doi.org/10.1111/j.1749-6632.1992.tb17080.x.

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30

Shiotani, Nobuhiro, Christine R. Bull, Roy N. West, Nobuo Kawamiya, Yasunori Kubo, and Shinya Wakoh. "Positron Annihilation in Ni3Ga." Journal of the Physical Society of Japan 55, no. 6 (June 15, 1986): 1961–70. http://dx.doi.org/10.1143/jpsj.55.1961.

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31

Jones, Goronwy Tudor. "Positron annihilation in flight." Physics Education 34, no. 5 (September 1999): 276–86. http://dx.doi.org/10.1088/0031-9120/34/5/302.

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32

Yamanaka, Chihiro, Kouji Hosokawa, Motoji Ikeya, Shigehiro Nishijima, and Toichi Okada. "Scanning Positron-Annihilation Microscope." Japanese Journal of Applied Physics 34, Part 1, No. 12A (December 15, 1995): 6528–29. http://dx.doi.org/10.1143/jjap.34.6528.

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33

Baranowski, A., M. Dębowska, K. Jerie, G. Mirkiewicz, J. Rudzińska-Girulska, and R. T. Sikorski. "Positron Annihilation in Chloropolystyrenes." Acta Physica Polonica A 83, no. 3 (March 1993): 239–49. http://dx.doi.org/10.12693/aphyspola.83.239.

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34

Andreeff, A. "Positron Annihilation in Chemistry." Zeitschrift für Physikalische Chemie 193, Part_1_2 (January 1996): 214. http://dx.doi.org/10.1524/zpch.1996.193.part_1_2.214.

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35

Belyanin, A. "Collective electron-positron annihilation." Physics Letters A 149, no. 5-6 (October 1, 1990): 258–64. http://dx.doi.org/10.1016/0375-9601(90)90425-n.

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36

Misheva, M., G. Toumbev, and M. Gospodinov. "Positron Annihilation in Bi12GeO20." Physica Status Solidi (a) 135, no. 1 (January 16, 1993): K9—K11. http://dx.doi.org/10.1002/pssa.2211350132.

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37

Misheva, M., P. Mishev, G. Pasajov, G. Toumbev, and R. Yakimova. "Positron annihilation in GaAs." Crystal Research and Technology 23, no. 3 (March 1988): 405–8. http://dx.doi.org/10.1002/crat.2170230322.

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38

Qin, Anwei, Xiaohe Chen, Yulian Pan, and Ll'ou Qiu. "POSITRON ANNIHILATION IN SIS." Chinese Journal of Applied Chemistry 4, no. 4 (August 1, 1987): 31–34. http://dx.doi.org/10.3724/j.issn.1000-0518.1987.4.31.

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39

Qin, Anwei, Xiaohe Chen, Yulian Pan, and Ll'ou Qiu. "POSITRON ANNIHILATION IN SIS." Chinese Journal of Applied Chemistry 4, no. 4 (August 1, 1987): 31–34. http://dx.doi.org/10.3724/j.issn.1000-0518.1987.4.3134.

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40

Liu, Meng, Jakub Čížek, Cynthia S. T. Chang, and John Banhart. "A Positron Study of Early Clustering in Al-Mg-Si Alloys." Materials Science Forum 794-796 (June 2014): 33–38. http://dx.doi.org/10.4028/www.scientific.net/msf.794-796.33.

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Early stages of clustering in quenched Al-Mg-Si alloys during natural ageing were studied by positron annihilation lifetime spectroscopy utilizing its unique sensitivity to electron density differences in various atomic defects. Two different positron trapping sites could be identified, one related to a vacancy-type defect, the other to solute clusters. The first trap is deep, i.e. irreversibly traps positrons, the second shallow, from which positrons can escape, which creates the signature of a temperature-dependent positron lifetime. During the first 80 min of NA, the vacancy-related contribution decreases, while the solute clusters increasingly trap positrons, thus reflecting their continuous growth and power to trap positrons. Coincident Doppler broadening spectroscopy of the annihilation radiation shows that the annihilation sites are Si-rich after quenching but contain more Mg after 70 min.

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41

Hirade, Tetsuya, Toshitaka Oka, Norio Morishita, Akira Idesaki, and Akihiko Shimada. "Positron Annihilation Lifetime of Irradiated Polyimide." Materials Science Forum 733 (November 2012): 151–54. http://dx.doi.org/10.4028/www.scientific.net/msf.733.151.

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Ortho-positronium pick off annihilation lifetime gives the information of the microscopic free volume of polymers. Polyimide polymers such as Kapton are applied in many fields, but it was impossible to apply the positron lifetime method for free volume investigation because of no positronium formation. Here, we apply the idea of the free positron annihilation probability that is sum of the probability of annihilation by the positron and electrons on the molecular chain where the positron localized and that for the annihilation with the electrons on the neighboring molecular chains. The second term is probably affected by the free volume change. We have successfully shown the temperature dependence and the electron beam irradiation effect on the free volume change by observing the free positron annihilation lifetime for Kapton.

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42

BAS, CORINE, N. DOMINIQUE ALBÉROLA, MARIE-FRANCE BARTHE, JÉRÉMIE De BAERDEMAEKER, and CHARLES DAUWE. "POSITRON INTERACTION IN POLYMERS." International Journal of Modern Physics A 19, no. 23 (September 20, 2004): 3951–59. http://dx.doi.org/10.1142/s0217751x04020208.

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A series of dense copolyimide membranes was characterized using positron annihilation spectroscopy. The positron annihilation lifetime spectroscopy performed on film with a classical positron source gives informations on the positronium fraction formed and also on the hole size within the film. The Doppler broadening spectra (DBS) of the gamma annihilation rays coupled with a variable energy positron beam allow the microstructural analyses as a function of the film depth. Experimental data were also linked to the chemical structure of the polyimides. It was found that the presence of the fluorine atoms strongly affects the positron annihilitation process and especially the DBS responses.

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43

Zhang, Yan Hui, Dong Wang, Chang Shu He, Xing Zhong Cao, and Lin Zhang. "Effect of Heat Treatment on Positron Annihilation Lifetime of an Extruded Al-12.7Si-0.7Mg Alloy." Materials Science Forum 788 (April 2014): 258–61. http://dx.doi.org/10.4028/www.scientific.net/msf.788.258.

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Positron annihilation lifetime can reflect the information of electronic density. Therefore this technique is very sensitive to the vacancies. Therefore positron annihilation technology (PAT) is a non-destructive testing technology for the investigation on the vacancy in pure metals and alloys. The vacancy defects of as-cast pure aluminium and the extruded Al-12.7Si-0.7Mg alloy before and after heat treatment were investigated by positron annihilation lifetime spectra. The results of positron annihilation lifetime spectra show that the lifetime of free positron annihilation in the pure aluminium alloy is 155 ps. The positron annihilation lifetime of the extruded sample is longer than the lifetime in the pure aluminium due to the formation of grain boundary and dislocation during the extrusion process. The positron annihilation lifetime of the extruded sample after heat treatment is shorter than that before the heat treatment, and it is longer than that of the pure sample.

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44

Guo, Wei Feng, Xiang Lei Chen, Huai Jiang Du, Hui Min Weng, and Bang Jiao Ye. "Positron Annihilation in Carbon Nanotubes." Materials Science Forum 607 (November 2008): 198–200. http://dx.doi.org/10.4028/www.scientific.net/msf.607.198.

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Positron annihilation lifetime spectra have been measured in carbon nanotubes being pressed as a function of pressure up to 1536MPa. In addition, positron lifetime experiments for carbon nanotubes in vacuum, nitrogen and air have been performed respectively. Lifetimes have been obtained using LIFETIME program. The results display a single-component positron annihilation lifetime. Positron lifetime for carbon nanotubes decreases as the pressure increases, but lifetime is basically consistent after the pressure of 960MPa. Positron annihilation lifetime for carbon nanotubes in air is the shortest whereas the lifetime in vacuum the longest. We conclude that a positron annihilates with an electron on the external surface of carbon nanotubes.

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45

Xu, Hong Xia, Jun Lin, Yu Chen, Bing Chuan Gu, Bang Jiao Ye, Zhi Yong Zhu, Hai Tao Jiang, Ya Juan Zhong, and Bing Liu. "Effect of FLiBe Infiltration Pressure on Microstructure of Matrix for TMSR Fuel Elements (FEs)." Defect and Diffusion Forum 373 (March 2017): 189–92. http://dx.doi.org/10.4028/www.scientific.net/ddf.373.189.

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The matrix graphite of fuel elements (FEs) with infiltration of 2LiF-BeF2(FLiBe) at different pressures varying from 0.4 MPa to 1.0 MPa, has been studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and positron annihilation lifetime (PAL) measurement. The result of XRD reveals that diffraction patterns of FLiBe appear in matrix graphite infiltrated with FLiBe at a pressure of 0.8 MPa and 1.0 MPa. The surface morphology from SEM shows that FLiBe mainly distributes within macro-pores of matrix graphite. PAL measurement indicates that there are mainly two positron lifetime components in all specimens:τ1~0.21 ns and τ2 ~0.47 ns, ascribed to annihilation of positrons in bulk and trapped-positrons at surface, respectively. The average positron lifetime decreases with infiltration pressure, due to the decrease in annihilation fraction of positrons with surface after infiltration of FLiBe into macro-pores.

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46

RATHORE, M. K., S. B. SHRIVASTAVA, V. RATHORE, K. P. JOSHI, and V. K. GUPTA. "POSITRON ANNIHILATION AT POLYMERIC SURFACES." Surface Review and Letters 11, no. 01 (February 2004): 41–48. http://dx.doi.org/10.1142/s0218625x04005822.

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The mechanism of slow positron annihilation at polymeric surfaces has been discussed in terms of positron diffusion at the surface and trapping of positrons and positronium in free volume holes. The one-dimensional diffusion equation has been solved and the rate equations have been set up to describe the various processes supposed to occur when a thermalized positron encounters the polymeric surface. The model has been used to calculate the Doppler broadening of the line shape parameter (S parameter) in polyurethane and polystyrene as a function of incident positron energy and temperature. The results have been compared with the available experimental data. The S parameter vs temperature curves show a remarkable discontinuity at the glass transition temperature (Tg). Large variation in the S parameter has been observed at low energies, suggesting a significant structure of free volume holes near the surface.

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47

John, Isabelle, and Tim Linden. "Cosmic-ray positrons strongly constrain leptophilic dark matter." Journal of Cosmology and Astroparticle Physics 2021, no. 12 (December 1, 2021): 007. http://dx.doi.org/10.1088/1475-7516/2021/12/007.

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Abstract Cosmic-ray positrons have long been considered a powerful probe of dark matter annihilation. In particular, myriad studies of the unexpected rise in the positron fraction have debated its dark matter or pulsar origins. In this paper, we instead examine the potential for extremely precise positron measurements by AMS-02 to probe hard leptophilic dark matter candidates that do not have spectral features similar to the bulk of the observed positron excess. Utilizing a detailed cosmic-ray propagation model that includes a primary positron flux generated by Galactic pulsars in addition to a secondary component constrained by He and proton measurements, we produce a robust fit to the local positron flux and spectrum. We find no evidence for a spectral bump correlated with leptophilic dark matter, and set strong constraints on the dark matter annihilation cross-section that fall below the thermal annihilation cross-section for dark matter masses below 60 GeV and 380 GeV for annihilation into τ+τ- and e+e-, respectively, in our default model.

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48

Trinh, Hoa Lang, Van Tao Chau, Hoang Lam Le, and Quoc Dung Tran. "Positron annihilation in mordenite zeolite." Nuclear Science and Technology 6, no. 1 (September 24, 2021): 50–55. http://dx.doi.org/10.53747/jnst.v6i1.146.

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The theoretical study of the positron annihilation in complex material such as zeolite is greatly significant to support and increase the accuracy analysis of the material structure from the experimental data of the positron annihilation. The mordenite zeolite is a big and complicated structure consisting of channels and cavities. The analysis of the mordenite structure is studied by the PALS so depending on the selection of the positron lifetime components of the positron annihilation spectra fitting methods. Therefore, these positron life times in on TO4, Na, Ca, K, Fe, H2O and the rings which form the channels and cavities are sophisticatedly studied by the DFT calculation using Ab-initio. The mordenite and modified mordenite zeolite structures are precisely analyzed, and the physical behaviors of the positron in these are more understood by these theoretical results.

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Wagner, Andreas, Wolfgang Anwand, Maik Butterling, Thomas E. Cowan, Fine Fiedler, Mathias Kempe, and Reinhard Krause-Rehberg. "Annihilation Lifetime Spectroscopy Using Positrons from Bremsstrahlung Production." Defect and Diffusion Forum 331 (September 2012): 41–52. http://dx.doi.org/10.4028/www.scientific.net/ddf.331.41.

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A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [ at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

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50

Young, J. A., and C. M. Surko. "Resonant Positron Annihilation on Molecules." Materials Science Forum 607 (November 2008): 9–16. http://dx.doi.org/10.4028/www.scientific.net/msf.607.9.

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At incident positron energies below the threshold for positronium atom formation, there are many cases in which annihilation rates for molecules are far in excess of that possible on the basis of simple two-body collisions. We now understand that this phenomenon is due to positron attachment to molecules mediated by vibrational Feshbach resonances. The attachment enhances greatly the overlap of the positron with molecular electrons and hence increases the probability of annihilation. Furthermore, measurements of the annihilation spectra as a function of incident positron energy provide a means of measuring positron-molecule binding energies. In this paper we present an overview of our current understanding of this process, highlighting key results and discussing outstanding issues that remain to be explained.

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