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Journal articles on the topic 'Processus radiatif collisionnel'

Author: Grafiati

Published: 4 June 2021

Last updated: 17 February 2022

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1

Seaton, M. J. "New Atomic Data for Astronomy: An Introductory Review." Highlights of Astronomy 10 (1995): 570–71. http://dx.doi.org/10.1017/s1539299600012065.

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Astronomers require the following basic atomic data: energy levels and wavelengths’, radiative transition probabilities; cross sections for photo-ionisation and for collisional processes; and line profile parameters. They also require processed data such as: level populations; opacities; radiation forces; line emissivities; and collisional rate-coefficients.Many of the data used by astronomers come from theoretical work. Experimental work is of importance in determining accurate wavelengths, in providing essential checks on theory for radiative probabilities and collision rates, and in the determination of line-profile parameters. Experimental studies are particularly important for processes of collisional ionisation.

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2

Peltz, Csaba, László Drahos, and Károly Vékey. "SORI excitation: Collisional and radiative processes." Journal of the American Society for Mass Spectrometry 18, no. 12 (December 2007): 2119–26. http://dx.doi.org/10.1016/j.jasms.2007.09.011.

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3

Bacchus-Montabonel, M. C. "Radiative and collisional processes in space chemistry." Rendiconti Lincei 22, no. 2 (February 22, 2011): 95–103. http://dx.doi.org/10.1007/s12210-011-0115-7.

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4

Lister, Graeme G. "Collisional and radiative processes in fluorescent lamps." Physics of Plasmas 10, no. 5 (May 2003): 2136–41. http://dx.doi.org/10.1063/1.1555829.

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5

Halpern, Joshua B., Yuhui Huang, and Tatiana Titarchuk. "Radiative and collisional processes in CNA 2? i." Astrophysics and Space Science 236, no. 1 (1996): 11–17. http://dx.doi.org/10.1007/bf00644317.

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6

Kogan, V. I., A. B. Kukushkin, and V. S. Lisitsa. "Kramers electrodynamics and electron-atomic radiative-collisional processes." Physics Reports 213, no. 1-2 (April 1992): 1–116. http://dx.doi.org/10.1016/0370-1573(92)90161-r.

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7

Bradshaw, Stephen J., and John Raymond. "Collisional and Radiative Processes in Optically Thin Plasmas." Space Science Reviews 178, no. 2-4 (March 15, 2013): 271–306. http://dx.doi.org/10.1007/s11214-013-9970-0.

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8

Copeland, Richard A., and David R. Crosley. "Radiative, collisional and dissociative processes in triplet acetone." Chemical Physics Letters 115, no. 4-5 (April 1985): 362–68. http://dx.doi.org/10.1016/0009-2614(85)85149-6.

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9

Becker, Kurt H., Peter F. Kurunczi, and Karl H. Schoenbach. "Collisional and radiative processes in high-pressure discharge plasmas." Physics of Plasmas 9, no. 5 (May 2002): 2399–404. http://dx.doi.org/10.1063/1.1449464.

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10

Martus, K., N. Masoud, and K. Becker. "Collisional and radiative processes in high-pressure Ne/N2discharges." Plasma Sources Science and Technology 15, no. 2 (April 26, 2006): S84—S90. http://dx.doi.org/10.1088/0963-0252/15/2/s11.

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11

Masnavi, Majid, and Martin Richardson. "Spectroscopic Studies of Laser-Based Far-Ultraviolet Plasma Light Source." Applied Sciences 11, no. 15 (July 27, 2021): 6919. http://dx.doi.org/10.3390/app11156919.

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A series of experiments is described which were conducted to measure the absolute spectral irradiances of laser plasmas created from metal targets over the wavelength region of 123–164 nm by two separate 1.0 μm lasers, i.e., using 100 Hz, 10 ns, 2–20 kHz, 60–100 ns full-width-at-half-maximum pulses. A maximum radiation conversion efficiency of ≈3%/2πsr is measured over a wavelength region from ≈125 to 160 nm. A developed collisional-radiative solver and radiation-hydrodynamics simulations in comparison to the spectra detected by the Seya–Namioka-type monochromator reveal the strong broadband experimental radiations which mainly originate from bound–bound transitions of low-ionized charges superimposed on a strong continuum from a dense plasma with an electron temperature of less than 10 eV.

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12

SASAKI, Akira. "Prospect on the Atomic and Molecular Processes in Plasmas. Collisional Radiative Model. Collisional Radiative Model for Complex Ions." Journal of Plasma and Fusion Research 75, no. 10 (1999): 1138–44. http://dx.doi.org/10.1585/jspf.75.1138.

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13

Lemal, A., C. M. Jacobs, M. Y. Perrin, C. O. Laux, P. Tran, and E. Raynaud. "Air Collisional-Radiative Modeling with Heavy-Particle Impact Excitation Processes." Journal of Thermophysics and Heat Transfer 30, no. 1 (January 2016): 226–39. http://dx.doi.org/10.2514/1.t4549.

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14

Demura, Alexander, Mikhail Kadomtsev, Valery Lisitsa, and Vladimir Shurygin. "Tungsten Ions in Plasmas: Statistical Theory of Radiative-Collisional Processes." Atoms 3, no. 2 (May 25, 2015): 162–81. http://dx.doi.org/10.3390/atoms3020162.

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15

ARNOLD, R. C. "COOLING OF INTENSE HEAVY-ION BEAMS BY COLLISIONAL-RADIATIVE PROCESSES." Le Journal de Physique Colloques 49, no. C7 (December 1988): C7–231—C7–235. http://dx.doi.org/10.1051/jphyscol:1988727.

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16

Kallenbach, A., M. Gunther, R. Kunnemeyer, and M. Kock. "Collisional and radiative processes in a laser-pumped barium vapour." Journal of Physics B: Atomic and Molecular Physics 19, no. 17 (September 14, 1986): 2645–58. http://dx.doi.org/10.1088/0022-3700/19/17/014.

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17

Nahar, Sultana N. "Atomic Processes in Planetary Nebulae." Symposium - International Astronomical Union 209 (2003): 325–34. http://dx.doi.org/10.1017/s0074180900208942.

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A hot central star illuminating the surrounding ionized H II region usually produces very rich atomic spectra resulting from basic atomic processes: photoionization, electron-ion recombination, bound-bound radiative transitions, and collisional excitation of ions. Precise diagnostics of nebular spectra depend on accurate atomic parameters for these processes. Latest developments in theoretical computations are described, especially under two international collaborations known as the Opacity Project (OP) and the Iron Project (IP), that have yielded accurate and large-scale data for photoionization cross sections, transition probabilities, and collision strengths for electron impact excitation of most astrophysically abundant ions. As an extension of the two projects, a self-consistent and unified theoretical treatment of photoionization and electron-ion recombination has been developed where both the radiative and the dielectronic recombination processes are considered in an unified manner. Results from the Ohio State atomic-astrophysics group, and from the OP and IP collaborations, are presented. A description of the electronic web-interactive database, TIPTOPBASE, with the OP and the IP data, and a compilation of recommended data for effective collision strengths, is given.

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18

SAWADA, Keiji. "Prospect on the Atomic and Molecular Processes in Plasmas. Collisional Radiative Mode. Collisional Radiative Model for Hydrogen Atom and Molecule." Journal of Plasma and Fusion Research 75, no. 10 (1999): 1132–37. http://dx.doi.org/10.1585/jspf.75.1132.

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19

Nikitović, Željka D., Aleksandra I. Strinić, Vladimir D. Stojanović, Gordana N. Malović, and Zoran Lj Petrović. "A Monte Carlo simulation of collisional processes in a Townsend discharge in neon." Radiation Physics and Chemistry 76, no. 3 (March 2007): 556–60. http://dx.doi.org/10.1016/j.radphyschem.2005.12.061.

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20

Gu, M. F. "The flexible atomic code." Canadian Journal of Physics 86, no. 5 (May 1, 2008): 675–89. http://dx.doi.org/10.1139/p07-197.

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We describe a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionization, autoionization; and their inverse processes radiative recombination and dielectronic capture. The atomic theoretical background and numerical techniques associated with each process are discussed in detail. Sample applications and results are presented. PACS Nos.: 31.15.–p, 32.70.Cs, 34.80.Kw, 32.80.Fb, 32.80.Dz

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21

Cornille, M., J. Dubau, M. Loulergue, and S. Jacquemot. "Spectroscopy in Ne-Like Plasmas. Z-Dependence of the Atomic Data Used in a Collisional-Radiative Model." International Astronomical Union Colloquium 102 (1988): 95–97. http://dx.doi.org/10.1017/s025292110010750x.

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AbstractThe Livermore X-ray Laser experiments in 1984 have shown the existence of Ne-like 3p-3s population inversions in a collisional Se plasma (Z=34) with significant gains (5 cm-1). We have focused our efforts on the behavior of the gains along the target neon Isoelectronic sequence. This study implies the determination of the Z-dependance of the rate coefficients of all the Involved atomic processes: collisional excitation (C). radiative decay (A) and dielectronic recombination (αd). Thus we use atomic structure and electron-ion collisional codes (SUPERSTRUCTURE. Distorted Waves. AUTOLSJ and JJOM). The different calculations have been done on a large selection of ions, from Ar to Ag. They Include relatlvistic effects in a fine structure scheme. The Z-dependance of the numerical results is expressed as polynomial or rational forms.

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22

Crowther, Paul A., Linda J. Smith, and Allan J. Willis. "The H/He Ratio of WN Stars." Symposium - International Astronomical Union 143 (1991): 97. http://dx.doi.org/10.1017/s0074180900044934.

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The observed He II Pickering decrement is modelled using the escape probability method developed by Castor & Van Blerkom (1970) to solve simultaneously the equations of radiative and statistical equilibrium for detailed model hydrogen and helium atoms. All important radiative and collisional processes are incorporated in this nLTE model. We confirm values of 0.0 ≤ H/He ≤ 0.5 for WNE stars and 0.0 ≤ H/He ≤ 3.0 for WNL stars with considerable spread in each subtype.

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23

Pietanza, L. D., G. Colonna, A. De Giacomo, and M. Capitelli. "Kinetic processes for laser induced plasma diagnostic: A collisional-radiative model approach." Spectrochimica Acta Part B: Atomic Spectroscopy 65, no. 8 (August 2010): 616–26. http://dx.doi.org/10.1016/j.sab.2010.03.012.

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24

Nahar, Sultana N. "The Iron Project and TIPTOPbase: Atomic Data and Opacities for Astrophysics." Symposium - International Astronomical Union 209 (2003): 335–36. http://dx.doi.org/10.1017/s0074180900208954.

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The Iron Project (IP) is an extension of the Opacity Project, an international collaboration of atomic physicists and astrophysicists. The aim of the IP is the development and application of new methods in theoretical atomic physics to the calculation of large-scale atomic data of high accuracy for radiative and collisional processes for astrophysically important elements.

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25

Chefai, A., N. E. Jaidane, K. Hammami, and F. Lique. "Fine and hyperfine excitation of CCN by He." Monthly Notices of the Royal Astronomical Society 497, no. 2 (July 13, 2020): 1862–69. http://dx.doi.org/10.1093/mnras/staa2058.

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ABSTRACT The relative abundance of cyanide and isocyanide molecules is a sensitive tracer of the physical conditions in the interstellar and circumstellar media. Accurate modelling of collisional and radiative processes implying these species opens the way for accurate estimation of their abundances. The present paper focuses on the computation of collisional rate coefficients for fine and hyperfine (de-)excitation of the CCN molecule (one of the C2N isomers) in collision with He, for temperatures up to 150 K. Using a time independent coupled-channel approach, scattering calculations were performed for transitions implying the lowest 56 fine structure levels and the corresponding 166 hyperfine structure levels belonging to both 2Π1/2 and 2Π3/2 spin-orbit manifolds. We provided, for the first time, realistic collisional data for the CCN radical. Propensity rules for fine and hyperfine transitions are discussed. As a first application, we evaluated the impact of these new data on the astrophysical modelling through radiative transfer calculations. We obtained the brightness and excitation temperatures of selected lines observed towards circumstellar envelopes and we found that local thermodynamic equilibrium conditions are not fulfilled for this species. As a consequence, our results indicate that the abundance of the CCN derived from the observations has to be revised since the observation modelling strongly depends on the collisional data used.

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26

Dalgarno, A., and S. Lepp. "Chemistry in the Early Universe." Symposium - International Astronomical Union 120 (1987): 109–20. http://dx.doi.org/10.1017/s0074180900153902.

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The chemical processes which led to the formation of molecules in the early universe are described. Molecular hydrogen is formed by two sequences. in one, radiative attachment to form H− is followed by associative detachment and in the other radiative association to form H2+ is followed by a chemical reaction with H. Trace amounts of HD and the molecular ion LiH+ are formed by the reaction of D+ with H2 and by the radiative association of Li+ and H. The H2 molecular fraction in the expanding universe is about 10−6.Because they are cooling agents, hydrogen molecules are significant in the collapse of pre-galactic clouds. With increasing density the hydrogen gas is converted to molecular hydrogen by three-body recombination and emission from the rotational and vibrational levels cools the cloud and slows the rise in temperature of the gravitationally collapsing object. Ultimately though, the radiation is trapped and the temperature rises. The H2 molecules are then destroyed by collision-induced dissociation. At still higher temperatures collisional ionization occurs, initiated most probably by the process of associative ionization.Molecules may be significant also in galaxy formation if the explosive amplification model is correct. Heavy elements may be present in the shell of gas swept up by the blast waves of the exploded seed galaxies and chemical processes leading to the formation of molecular hydrides may take place, in a scenario analogous to the aftermath of an interstellar dissociative shock.

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27

Vassie, L. H., and H. H. Telle. "Radiative Lifetimes and Collision Processes in Sodium-Rare Gas and Sodium-Hydrogen Systems." Laser Chemistry 15, no. 1 (January 1, 1994): 1–19. http://dx.doi.org/10.1155/1994/74032.

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Investigations of the collisional interactions between sodium atoms in the 32P states and helium and hydrogen gases are described. Studies of collision-induced mixing and quenching interactions have been carried out under conditions where chemical reaction to produce sodium hydride is possible. Thus the sodium number derivatives are sufficient for radiation trapping to occur. This is in contrast to virtually all previous investigations in which conditions were such that this effect need not be considered. The intensity and temporal behaviour of laser induced fluorescence (LIF) resulting from the photoexcitation of the sodium 32P states is monitored as a function of foreign gas pressure. Whilst many of the features observed are to be expected, results show how radiation trapping strongly influences cross-section determination. The need for a more rigorous treatment of collision cross-sections under these conditions, which are often more realistic than the ‘ideal’ trapping free situations, is demonstrated.

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28

Kodama, R. "Study of X-ray laser interaction plasmas." Laser and Particle Beams 10, no. 4 (December 1992): 821–26. http://dx.doi.org/10.1017/s0263034600004778.

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Atomic processes in X-ray laser interaction plasmas are investigated by using a collisional-radiative model. Population inversions on free-bound transitions can be produced by photoionization above a threshold of incident X-ray laser intensity and lead to stimulated free-bound emission (SFBE). Free-bound lasers pumped by intense X-ray lasers are proposed and their feasibility is investigated simply considering X-ray laser interaction plasmas.

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29

Demura, A. V., M. B. Kadomtsev, V. S. Lisitsa, and V. A. Shurygin. "Universal statistical approach to radiative and collisional processes with multielectron ions in plasmas." High Energy Density Physics 15 (June 2015): 49–58. http://dx.doi.org/10.1016/j.hedp.2015.03.006.

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30

Itoh, M., T. Yabe, and S. Kiyokawa. "Collisional-radiative and average-ion hybrid models for atomic processes in high-Zplasmas." Physical Review A 35, no. 1 (January 1, 1987): 233–41. http://dx.doi.org/10.1103/physreva.35.233.

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31

Autrique, D., I. Gornushkin, V. Alexiades, Z. Chen, A. Bogaerts, and B. Rethfeld. "Revisiting the interplay between ablation, collisional, and radiative processes during ns-laser ablation." Applied Physics Letters 103, no. 17 (October 21, 2013): 174102. http://dx.doi.org/10.1063/1.4826505.

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32

Hong, Qizhen, Xiaoyong Wang, Yuan Hu, Xin Lin, and Quanhua Sun. "Rebuilding experimental nonequilibrium radiation in shock-heated Martian-like mixture flows using electronic state-to-state approach." International Journal of Modern Physics B 34, no. 14n16 (May 30, 2020): 2040084. http://dx.doi.org/10.1142/s0217979220400846.

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An electronic state-to-state approach is developed to reproduce numerically the radiative processes in the experiments on the Electric Arc Shock Tube facility at NASA Ames Research Center. The experiments measured the spectral radiance of C2 Swan band and CO 4th Positive band behind the strong shock wave in a Martian-like mixture. The present state-to-state approach solves the electronic states of strong radiators by integrating the collisional-radiative model into the master equations in the frame of Euler equations. Particularly, the electron impact dissociation of CO is included, and the rate coefficients are proposed for the electronic state-specific heavy-particle impact excitation and dissociation of C2. The nonequilibrium radiation behind the shock is calculated by the line-by-line method, and it is then convoluted using the calibrated smearing function in order to compare with the experiments. The state-specific simulation results is found to agree well with both spectral and spatial measurement data. The simulated electronic state populations of CO and C2 deviate from Boltzmann distributions significantly, which could explain the failure of previous two-temperature quasi-steady-state based simulations.

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33

DAVIS, J., R. CLARK, M. BLAHA, and J. L. GIULIANI. "Atomic physics and non-LTE effects." Laser and Particle Beams 19, no. 4 (October 2001): 557–77. http://dx.doi.org/10.1017/s0263034601194048.

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Pulsed-power-driven z-pinch plasmas are an intense source of soft X-ray radiation producing, on the Z facility, about 2 MJ of total radiation for a number of tungsten loads and in the case of a multiwire titanium array over 1 MJ total radiation and about 100 kJ from the titanium K-shell. The production and transport of radiation in these non-LTE plasmas are often modeled assuming some variation of Local Thermodynamic Equilibrium (LTE) in conjunction with radiation diffusion. Since these plasmas are neither in LTE or entirely opaque or transparent these models do not properly predict the emitted radiation spectra and yield. Also, application of these models overestimates the radiation cooling to the extent that the evolving hydrodynamic profiles are significantly different from those that would obtain using the appropriate non-LTE model with a more realistic treatment of the radiation transport. In this investigation, we discuss the production and transport of radiation from the viewpoint of the microscopic collisional and radiative processes and then apply it to z-pinch plasmas. Through the use of examples and illustrations, it is shown that for identical initial load conditions, atomic level structure, and rate coefficients, the models predict different results that affect the dynamic evolution and hydrodynamic history of the plasma. As an example, the emission spectrum is generated using a 1-D radiation MHD model self-consistently coupled to a circuit representing the Sandia Z facility. A comparison is then made between several standard models of ionization dynamics for a multiwire titanium array. Finally, we address some of the issues regarding how the dense plasma environment influences isolated atom structure and processes. These include, for example, atomic level shifts, ionization lowering, collision cross sections, and collision widths. Transition from the isolated-atom to the dressed-particle picture can modify the ionization physics and emission spectra to such an extent that it may challenge our precepts on how best to design loads for the next generation machine.

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34

Minoo, H., M. Cukier, and J. Haidar. "Time-dependent collisional radiative model of ionizing and recombining plasmas." Laser and Particle Beams 8, no. 4 (December 1990): 697–708. http://dx.doi.org/10.1017/s0263034600009095.

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A time-dependent collisional radiative model, based on a five-charge state at any spacetime point in the plasma, is elaborated in order to follow the basic atomic physics processes in a plasma undergoing ionization and recombination. This model can either be used independently or be included in a magnetohydrodynamics code of a transient plasma. In the latter case, the efficiency of the model makes it particularly useful in saving computing time of hydrodynamic codes developed in connection with ion-driven fusion.

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35

Marinković, Bratislav, Vladimir Srećković, Veljko Vujčić, Stefan Ivanović, Nebojša Uskoković, Milutin Nešić, Ljubinko Ignjatović, Darko Jevremović, Milan Dimitrijević, and Nigel Mason. "BEAMDB and MOLD—Databases at the Serbian Virtual Observatory for Collisional and Radiative Processes." Atoms 7, no. 1 (January 14, 2019): 11. http://dx.doi.org/10.3390/atoms7010011.

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In this contribution we present a progress report on two atomic and molecular databases, BEAMDB and MolD, which are web services at the Serbian virtual observatory (SerVO) and nodes within the Virtual Atomic and Molecular Data Center (VAMDC). The Belgrade Electron/Atom (Molecule) DataBase (BEAMDB) provides collisional data for electron interactions with atoms and molecules. The Photodissociation (MolD) database contains photo-dissociation cross sections for individual rovibrational states of diatomic molecular ions and rate coefficients for the chemi-ionisation/recombination processes. We also present a progress report on the major upgrade of these databases and plans for the future. As an example of how the data from the BEAMDB may be used, a review of electron scattering from methane is described.

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36

Roueff, Evelyne, and François Lique. "Molecular Excitation in the Interstellar Medium: Recent Advances in Collisional, Radiative, and Chemical Processes." Chemical Reviews 113, no. 12 (October 16, 2013): 8906–38. http://dx.doi.org/10.1021/cr400145a.

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37

Lebedev, V. S., and V. S. Marchenko. "Collisional and radiative processes with participation of highly excited states of atoms and molecules." Journal of Soviet Laser Research 7, no. 5 (1986): 489–534. http://dx.doi.org/10.1007/bf01120342.

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38

Dimitrijević, Milan S., Vladimir A. Srećković, Alaa Abo Zalam, Nikolai N. Bezuglov, and Andrey N. Klyucharev. "Dynamic Instability of Rydberg Atomic Complexes." Atoms 7, no. 1 (February 8, 2019): 22. http://dx.doi.org/10.3390/atoms7010022.

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Atoms and molecules in highly excited (Rydberg) states have a number of unique characteristics due to the strong dependence of their properties on the values of principal quantum numbers. The paper discusses the results of an investigation of collisional Rydberg complexes specific features, resulting in the development of dynamic chaos and the accompanying diffusion autoionization processes. It is shown (experiment and theory) that, in subthermal low energies, the global chaotic regime that evolved in quasimolecular systems leads to significant changes in the Rydberg gases radiation/ionization kinetics. The effect of Förster resonance on the width of the fluorescence spectra and stochastic ionization processes in Rydberg systems is also discussed.

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39

Geballe, T. R. "Infrared spectroscopy of molecular hydrogen in astrophysical environments." Canadian Journal of Physics 72, no. 11-12 (November 1, 1994): 782–85. http://dx.doi.org/10.1139/p94-102.

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Forty-five years ago Gerhard Herzberg became the first person to observe lines of the infrared rotation–vibration bands of molecular hydrogen; 20 years ago astronomers first found some of these lines in the interstellar medium. Examples are given of astrophysical environments in which H2 has been detected, with emphasis on their growing importance to astronomy. The rotation–vibration spectrum has been observed in emission following both collisional and radiative excitation processes. Recent detections of absorption by cold interstellar molecular hydrogen, both in the gaseous and the solid states, have expanded knowledge of physical properties of molecular clouds and the physical and chemical processes occurring within them.

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40

Borysow, Aleksandra. "Pressure-Induced Molecular Absorption in Stellar Atmospheres." International Astronomical Union Colloquium 146 (1994): 209–22. http://dx.doi.org/10.1017/s0252921100021345.

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Pressure-induced absorption arises in complexes of two or more inert atoms or molecules, due to dipole moments induced during the collisional interaction. The term “pressure-induced” still prevails in the astrophysical literature, yet “collision-induced” absorption (CIA), or “interaction-induced” absorption seems more appropriate and is commonly used elsewhere. Ordinary absorption processes in the infrared arise from individual, polar molecules interacting with electromagnetic radiation. As a consequence, the intensity of the allowed lines increases linearly with density. CIA, on the other hand, is most striking in gases composed of nonpolar, infrared-inactive molecules. Induced spectral lines are observed at rovibrational frequencies which are dipole-forbidden in single (i.e. non-interacting) molecules. Dipole transitions may, however, beinducedin the interacting pair. The new symmetry of the electronic cloud of a collisional complex may be very different from those of the isolated molecules and thus commonly allows for a transient dipole, which then interacts with radiation. Collision-induced absorption increases quadratically in the low density limit, thus reflecting the two-body origin of the basic absorption process. At higher gas densities, ternary interactions become significant and cubic and higher-order contributions to the observable absorption are then commonly seen.

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41

Carpenter, K. G. "Fluorescence in the Outer Atmospheres of Red Giant Stars." International Astronomical Union Colloquium 106 (1989): 372. http://dx.doi.org/10.1017/s0252921100063302.

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The outer atmosphere of a cool red giant star is an ideal locale for the operation of line fluorescence processes. Low plasma densities imply low rates of collisional de-excitation and thus allow radiative decay of levels populated by selective radiative pumping. There are many strong sources of line radiation (i.e. possible pumps) and numerous possible upward transitions from highly populated low-lying levels of abundant elements such as Fe II, thus providing many chance coincidences between potential pumps and lines to be pumped. These conditions ensure that many of the chromospheric emission features observed in the UV spectrum of such a star are affected by fluorescence. Many of the observed emission features originate from energy levels populated solely by radiative fluorescent excitation, including strong lines of S I, O I, CO, Ni II, Si I, Fe I and Fe II, as well as weaker lines from Cr II and Co II. Important pumps active in these atmospheres include hydrogen Lyman alpha, and individual lines of 0 I, C I, Si II, Fe II, and Mg II. In the case of Fe II, there are many additional features arising from upper levels whose populations, although primarily maintained by collisions, are also significantly affected by radiative fluorescent excitation. In fact, there may be virtually no level in Fe II not affected to one degree or another by direct decays or cascades down from levels populated by fluorescence, driven either by Lyman alpha or, in some cases, by lines of Fe II itself (“self-fluorescence“).

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42

Del Zanna, Giulio, and Peter R. Young. "Atomic Data for Plasma Spectroscopy: The CHIANTI Database, Improvements and Challenges." Atoms 8, no. 3 (August 20, 2020): 46. http://dx.doi.org/10.3390/atoms8030046.

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CHIANTI is an atomic database and software package for modeling emission lines and continua from hot astrophysical plasmas. It is freely available to all researchers and has been widely used in the Heliophysics and Astrophysics communities for almost 25 years. In this review, we summarize the properties of the current version of the database and give an overview of the relevant atomic processes. We also discuss progress towards a complete implementation of collisional-radiative modeling, simultaneously solving for atomic level and ion populations for individual elements.

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Dasgupta, A., R. W. Clark, J. Davis, and J. L. Giuliani. "Impact of atomic collisional and radiative processes on modeling and spectroscopy of highly ionized plasma." Journal of Physics: Conference Series 194, no. 15 (November 1, 2009): 152020. http://dx.doi.org/10.1088/1742-6596/194/15/152020.

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Bilbao, L., H. A. Bruzzone, and H. J. Kelly. "Influence of collisional and radiative processes in the structure of a plasma focus current sheath." Plasma Physics and Controlled Fusion 27, no. 11 (November 1, 1985): 1207–15. http://dx.doi.org/10.1088/0741-3335/27/11/001.

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Taylor, M. L., R. D. Franich, J. V. Trapp, and P. N. Johnston. "Electron Interaction with Gel Dosimeters: Effective Atomic Numbers for Collisional, Radiative and Total Interaction Processes." Radiation Research 171, no. 1 (January 2009): 123–26. http://dx.doi.org/10.1667/rr1438.1.

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Foster, Adam R., and Keri Heuer. "PyAtomDB: Extending the AtomDB Atomic Database to Model New Plasma Processes and Uncertainties." Atoms 8, no. 3 (August 24, 2020): 49. http://dx.doi.org/10.3390/atoms8030049.

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The AtomDB project provides models of X-ray and extreme ultraviolet emitting astrophysical spectra for optically thin, hot plasma. We present the new software package, PyAtomDB, which now underpins the entire project, providing access to the underlying database, collisional radiative model calculations, and spectrum generation for a range of models. PyAtomDB is easily extensible, allowing users to build new tools and models for use in analysis packages such as XSPEC. We present two of these, the kappa and ACX models for non-Maxwellian and Charge-Exchange plasmas respectively. In addition, PyAtomDB allows for full open access to the apec code, which underlies all of the AtomDB spectra and has enabled the development of a module for estimating the sensitivity of emission lines and diagnostic line ratios to uncertainties in the underlying atomic data. We present these publicly available tools and results for several X-ray diagnostics of Fe L-shell ions and He-like ions as examples.

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Volk, Kevin, and Sun Kwok. "A self-consistent photoionization-dust continuum-molecular line transfer model of NGC7027." Symposium - International Astronomical Union 180 (1997): 285. http://dx.doi.org/10.1017/s007418090013102x.

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A model to simulate the entire spectrum (1000 Å to 1 cm) of the high-excitation young planetary nebula NGC 7027 is presented. The ionized, dust, and molecular components of the object are modeled using geometric parameters obtained from visible, radio, infrared, and CO data. The physical processes considered include recombination lines of H and He, collisional excited lines of metals, bf and ff continuum radiations, two-photon radiation, dust continuum radiation, and molecular rotational and vibrational transitions. The dust component is assumed to be heated by a combination of direct starlight and the line and continuum radiation from the ionized nebula. The molecular component of the nebula is coupled to the dust component through the stimulated absorption of the dust continuum radiation. Specifically, we compare the predicted fluxes of the CO rotational lines and the 179.5 μm water rotational line to those observed by the Infrared Space Observatory satellite (Liu et al. 1996, A&A in press).

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Jacobs, V. L., and P. Beiersdorfer. "Kα X-ray emission spectra from highly charged Fe ions in EBIT." Canadian Journal of Physics 86, no. 1 (January 1, 2008): 217–30. http://dx.doi.org/10.1139/p07-104.

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A detailed spectral model has been developed for the computer simulation of the 2p → 1s Kα X-ray emission from highly charged Fe ions in the electron beam ion trap (EBIT). The spectral features of interest occur in the range 1.84–1.94 Å. The fundamental radiative emission processes associated with radiationless electron capture or dielectronic recombination, inner-shell electron collisional excitation, and inner-shell-electron collisional ionization are taken in account. For comparison, spectral observations and simulations for high-temperature magnetic-fusion (tokamak) plasmas are reviewed. In these plasmas, small departures from steady-state corona-model charge-state distributions can occur because of ion transport processes, while the assumption of equilibrium (Maxwellian) electron energy distributions is expected to be valid. Our investigations for EBIT have been directed at the identification of spectral features that can serve as diagnostics of extreme nonequilibrium or transient ionization conditions, and allowance has been made for general (non-Maxwellian) electron energy distributions. For the precise interpretation of the high-resolution X-ray observations, which may involve the analysis of blended spectral features composed of many lines, it has been necessary to take into account the multitude of individual fine-structure components of the Kα radiative transitions in the ions from Fe XVIII to Fe XXV. At electron densities higher than the validity range of the corona-model approximation, collisionally induced transitions among low-lying excited states can play an important role. It is found that inner-shell-electron excitation and ionization processes involving the complex intermediate ions from Fe XVIII to Fe XXI produce spectral features, in the wavelength range from 1.89 to 1.94 Å, which are particularly sensitive to density variations and transient ionization conditions. PACS Nos.: 52.72.+v, 32.80.Dz, 32.70.Fw, 32.30.Rj

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Aschwanden, M. J., L. Fletcher, T. Sakao, T. Kosugi, and H. Hudson. "Electron Trapping and Precipitation in Asymmetric Solar Flare Loops." Symposium - International Astronomical Union 195 (2000): 375–76. http://dx.doi.org/10.1017/s0074180900163168.

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Acceleration, propagation, and energy loss of particles energized in solar flares cannot be studied separately because their radiative signatures observed in the form of hard X-ray bremsstrahlung or radio gyrosynchrotron emission represent a convolution of all these processes. We analyze hard X-ray emission from solar flares using a kinematic model that includes free-streaming electrons (having an energy-dependent time-of-flight delay) as well as temporarily trapped electrons (which are pitch-angle scattered by Coulomb collisional scattering) to determine various physical parameters (trapping times, flux asymmetry, loss-cone angles, magnetic mirror ratios) in flare loops with asymmetric magnetic fields.

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Baeva, Margarita, Ralf Methling, and Dirk Uhrlandt. "Unified modelling of TIG microarcs with evaporation from copper anode." PLASMA PHYSICS AND TECHNOLOGY 8, no. 1 (March 11, 2021): 1–4. http://dx.doi.org/10.14311/ppt.2021.1.1.

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A previously developed unified model of a tungsten-inert gas (TIG) microarc has been extended to take into account the melting of the anode made of copper and the release of copper atoms due to its evaporation. The copper atoms enter the plasma to become excited and ionized. The presence of copper atoms and ions can strongly change the plasma parameters. The extended unified model further includes excited states of copper and collisional and radiative processes between them. Predictions of the parameters of the microarc plasma in the presence of copper species are presented and discussed.

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