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Journal articles on the topic 'Collision radiative'

Author: Grafiati

Published: 4 June 2021

Last updated: 4 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

Mioc, V., and C. Blaga. "Binary collisions in popovici’s photogravitational model." Serbian Astronomical Journal, no. 165 (2002): 9–16. http://dx.doi.org/10.2298/saj0265009m.

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The dynamics of bodies under the combined action of the gravitational attraction and the radiative repelling force has large and deep implications in astronomy. In the 1920s, the Romanian astronomer Constantin Popovici proposed a modified photogravitational law (considered by other scientists too). This paper deals with the collisions of the two-body problem associated with Popovici?s model. Resorting to McGehee-type transformations of the second kind, we obtain regular equations of motion and define the collision manifold. The flow on this boundary manifold is wholly described. This allows to point out some important qualitative features of the collisional motion: existence of the black-hole effect, gradientlikeness of the flow on the collision manifold, regularizability of collisions under certain conditions. Some questions, coming from the comparison of Levi-Civita?s regularizing transformations and McGehee?s ones, are formulated.

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3

Débarre, A., and Ph Cahuzac. "On the radiative-collision processes." Annales de Physique 12, no. 4 (1987): 313–45. http://dx.doi.org/10.1051/anphys:01987001204031300.

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4

van der Tak, Floris. "Radiative Transfer and Molecular Data for Astrochemistry." Proceedings of the International Astronomical Union 7, S280 (June 2011): 449–60. http://dx.doi.org/10.1017/s1743921311025191.

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AbstractThe estimation of molecular abundances in interstellar clouds from spectroscopic observations requires radiative transfer calculations, which depend on basic molecular input data. This paper reviews recent developments in the fields of molecular data and radiative transfer. The first part is an overview of radiative transfer techniques, along with a “road map” showing which technique should be used in which situation. The second part is a review of measurements and calculations of molecular spectroscopic and collisional data, with a summary of recent collisional calculations and suggested modeling strategies if collision data are unavailable. The paper concludes with an overview of future developments and needs in the areas of radiative transfer and molecular data.

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5

ZHONG-CAI, YUAN, SHI JIA-MING, WU XIAO-PO, and CHEN ZONG-SHEN. "Electro-physical property of plasma jet generated by burning chemicals as antenna." Journal of Plasma Physics 79, no. 1 (November 23, 2012): 51–54. http://dx.doi.org/10.1017/s0022377812000682.

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AbstractThe application of pulsed power to transient radiofrequency/microwave radiation for warhead/projectile payloads is currently a significant area of research. In this paper, the far-field radiative property of a plasma antenna is analyzed. Then, a plasma jet is generated by burning chemicals, in which the electron concentration and collision frequency are diagnosed, and the electric conductance is calculated. Finally, the feasibility to apply the plasma jet as antenna is investigated by analyzing the radiative pattern. The dependency of pattern on plasma electron density, collision frequency, and plasma wake radius is calculated and analyzed.

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6

Miraglia, Jorge E. "Radiative electron capture in proton-hydrogen collision." Physical Review A 32, no. 5 (November 1, 1985): 2702–6. http://dx.doi.org/10.1103/physreva.32.2702.

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7

Xi-Hua, Yang, Sun Zhen-Rong, Ding Liang-En, and Wang Zu-Geng. "Constructive interference via collision-aided radiative excitation." Chinese Physics 11, no. 4 (March 26, 2002): 346–51. http://dx.doi.org/10.1088/1009-1963/11/4/307.

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8

Stuchlik, Zdenek, and Jan Schee. "ON OBSERVATIONAL PHENOMENA RELATED TO KERR SUPERSPINARS." Acta Polytechnica 54, no. 3 (June 27, 2014): 254–58. http://dx.doi.org/10.14311/ap.2014.54.0254.

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We investigate possible signatures of a Kerr naked singularity (superspinar) in various observational phenomena. It has been shown that Kerr naked singularities (superspinars) have to be efficiently converted to a black hole due to accretion from Keplerian discs. In the final stages of the conversion process the near-extreme Kerr naked singularities (superspinars) provide a variety of extraordinary physical phenomena. Such superspinning Kerr geometries can serve as an efficient accelerator for extremely high-energy collisions, enabling a direct and clear demonstration of the outcomes of the collision processes. We shall discuss the efficiency and the visibility of the ultra-highenergy collisions in the deepest parts of the gravitational well of superspinning near-extreme Kerr geometries for the whole variety of particles freely falling from infinity. We demonstrate that ultrahigh-energy processes can be obtained with no fine tuning of the motion constants and the products of<br />the collision can escape to infinity with efficiency substantially higher than in the case of near-extreme black holes. Such phenomena influence the radiative processes taking place in the accretion disc, and together with the particular generated geometry they influence the observed radiation field. Here we<br />assume the “geometrical” influence of a Kerr naked singularity on the spectral line profiles of radiation emitted by monochromatically and isotropically radiating point sources forming a Keplerian ring or disc around such a compact object. We have found that the profiled spectral line of the radiating<br />Keplerian ring can be split into two parts because there is no event horizon in the naked singularity spacetimes. The profiled lines generated by Keplerian discs are qualitatively different for a Kerr naked singularity and black hole spacetimes broadened near the inner edge of a Keplerian disc.

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9

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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10

Iwabuchi, Hironobu. "Efficient Monte Carlo Methods for Radiative Transfer Modeling." Journal of the Atmospheric Sciences 63, no. 9 (September 1, 2006): 2324–39. http://dx.doi.org/10.1175/jas3755.1.

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Abstract Demands for Monte Carlo radiative transfer modeling have grown with the increase in computational power in recent decades. This method provides realistic simulations of radiation processes for various types of application, including radiation budgets in cloudy conditions and remote measurements of clouds, aerosols, and gases. Despite many advantages, such as explicit treatment of three-dimensional radiative transfer, issues of numerical efficiency can make the method intractable, especially in radiance calculations. The commonly used local estimation method requires computationally intensive ray tracing at each collision. Furthermore, the realistic phase function of Mie scattering by cloud and aerosol particles has very sharp peaks in the forward direction. Radiance computations by Monte Carlo methods are inefficient for such spiky phase functions because of significant noise. Moreover, in optically thin regions, sampling of radiance contributions is so rare that long computing times are required to reduce noise. To solve these issues, several variance reduction methods have been proposed. This paper discusses a modified local estimation method, a truncation approximation for a highly anisotropic phase function, a collision-forcing method for optically thin media, a numerical diffusion technique, and several related topics. Numerical experiments demonstrated significant improvements in efficiency for solar radiance calculations in a limited number of cloudy cases.

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11

Aggarwal, Kanti M., and Francis P. Keenan. "Radiative Rates, Collision Strengths and Effective Collision Strengths for Transitions in Mo XXXIV." Physica Scripta 71, no. 3 (January 1, 2005): 251–60. http://dx.doi.org/10.1238/physica.regular.071a00251.

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12

Aggarwal, K. M., F. P. Keenan, R. Kisielius, P. H. Norrington, R. E. King, G. J. Pert, and S. J. Rose. "Radiative Rates, Collision Strengths and Effective Collision Strengths for Transitions in Gd XXXVII." Physica Scripta 71, no. 4 (January 1, 2005): 356–61. http://dx.doi.org/10.1238/physica.regular.071a00356.

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13

Kadhim, Rashid O. "Study of Collision and Radiative Stopping Power of Electron for Blood, Bone, and Adipose Tissue." International Journal of Psychosocial Rehabilitation 24, no. 5 (April 20, 2020): 4386–91. http://dx.doi.org/10.37200/ijpr/v24i5/pr2020154.

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14

Regemorter, H. van, and N. Feautrier. "Non-adiabatic effects in collision-induced radiative transitions." Journal of Physics B: Atomic and Molecular Physics 18, no. 13 (July 14, 1985): 2673–91. http://dx.doi.org/10.1088/0022-3700/18/13/017.

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15

Rogers, D. W. O., and Reid W. Townson. "On calculating kerma, collision kerma and radiative yields." Medical Physics 46, no. 11 (September 20, 2019): 5173–84. http://dx.doi.org/10.1002/mp.13744.

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16

Li, S. M., Z. J. Chen, Q. Q. Wang, and Z. F. Zhou. "Laser influence on positron-antiproton radiative capture collision." European Physical Journal D - Atomic, Molecular and Optical Physics 7, no. 1 (August 1, 1999): 39–44. http://dx.doi.org/10.1007/s100530050345.

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17

Allard, Nicole F., John F. Kielkopf, Siyi Xu, Grégoire Guillon, Bilel Mehnen, Roberto Linguerri, Muneerah Mogren Al Mogren, Majdi Hochlaf, and Ivan Hubeny. "H–He collision-induced satellite in the Lyman α profile of DBA white dwarf stars." Monthly Notices of the Royal Astronomical Society 494, no. 1 (March 13, 2020): 868–75. http://dx.doi.org/10.1093/mnras/staa707.

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ABSTRACT The spectra of helium-dominated white dwarf stars with hydrogen in their atmosphere present a distinctive broad feature centred around 1160 Å in the blue wing of the Lyman α line. It is extremely apparent in WD 1425+540 recently observed with Hubble Space Telescope(HST) Cosmic Origins Spectrograph (COS). With new theoretical line profiles based on ab initio atomic interaction potentials we show that this feature is a signature of a collision-induced satellite due to an asymptotically forbidden transition. This quasi-molecular spectral satellite is crucial to understanding the asymmetrical shape of Lyman α seen in this and other white dwarf spectra. Our previous work predicting this absorption feature was limited by molecular potentials that were not adequate to follow the atomic interactions with spectroscopic precision to the asymptotic limit of large separation. A new set of potential energy curves and electronic dipole transition moments for the lowest electronic states of the H–He system were developed to account accurately for the behaviour of the atomic interactions at all distances, from the chemical regime within 1 Å out to where the radiating H atoms are not significantly perturbed by their neighbours. We use a general unified theory of collision-broadened atomic spectral lines to describe a rigorous treatment of hydrogen Lyman α with these potentials and present a new study of its broadening by radiative collisions of hydrogen and neutral helium. These results enable ab initio modelling of radiative transport in DBA white dwarf atmospheres.

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18

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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19

KAWATSURA, K., T. HASEGAWA, N. TERAZAWA, S. ARAI, M. SATAKA, H. NARAMOTO, K. KOMAKI, and A. OOTUKA. "CONTINUUM X RAYS IN HIGHLY CHARGED ION-ATOM COLLISIONS." International Journal of PIXE 06, no. 03n04 (January 1996): 441–45. http://dx.doi.org/10.1142/s0129083596000478.

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Continuous X rays produced by highly charged heavy ion-atom collisions have been studied experimentally. 2–5.5 MeV/u F, Si, S and Cl ions with zero or one electron were bombarded with a thin gas target of H 2 and He. Emitted X-ray spectra were measured by using a Si(Li) X-ray detector at 90°. The characteristic X rays and radiative electron capture X rays were observed clearly, which were superimposed on the continuum X rays. The continuum X rays can be well explained by two types of radiative processes: mainly quasi-free electron bremsstrahlung (QFEB), and partly atomic bremsstrahlung (AB). It should be noticed that QFEB is predominant at low X-ray energy region and AB at high X-ray energy region in highly charged heavy ion-atom collision process.

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20

Pavón, Diego, and Roberto A. Sussman. "Relaxation versus collision times in the cosmological radiative era." Classical and Quantum Gravity 18, no. 9 (April 6, 2001): 1625–36. http://dx.doi.org/10.1088/0264-9381/18/9/302.

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21

Bautista, M. A., P. Quinet, P. Palmeri, N. R. Badnell, J. Dunn, and N. Arav. "Radiative transition rates and collision strengths for Si II." Astronomy & Astrophysics 508, no. 3 (November 4, 2009): 1527–37. http://dx.doi.org/10.1051/0004-6361/200913179.

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22

Kivshar, Y. S., and B. A. Malomed. "Perturbation-induced radiative losses in collision of NSE solitons." Journal of Physics A: Mathematical and General 19, no. 16 (November 11, 1986): L967—L971. http://dx.doi.org/10.1088/0305-4470/19/16/004.

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23

Fannin, H. B., D. C. Miller, and C. J. Seliskar. "A Simple Kinetic Model for a Helium ICP." Applied Spectroscopy 41, no. 2 (February 1987): 173–76. http://dx.doi.org/10.1366/000370287774986778.

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A simple kinetic model is proposed to describe the population of the n3P and n1P states of helium for principle quantum numbers, n, from 3 to 10 in a 27-MHz ICP. The model incorporates two decay channels, namely those of radiative decay and collisional relaxation, to simulate the population. The functional form of the collision probability is approximated with the use of the Rydberg cross sections for the principal quantum number of the state. Experimental results are presented and are consistent with this model.

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24

Ohmura, Takumi, Mami Machida, Kenji Nakamura, Yuki Kudoh, Yuta Asahina, and Ryoji Matsumoto. "Two-Temperature Magnetohydrodynamics Simulations of Propagation of Semi-Relativistic Jets." Galaxies 7, no. 1 (January 11, 2019): 14. http://dx.doi.org/10.3390/galaxies7010014.

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In astrophysical jets observed in active galactic nuclei and in microquasars, the energy exchange rate by Coulomb collision is insufficient for thermal equilibrium between ions and electrons. Therefore, it is necessary to consider the difference between the ion temperature and the electron temperature. We present the results of two-temperature magnetohydrodynamics(MHD) simulations to demonstrate the effects of Coulomb coupling. It is assumed that the thermal dissipation heats only ions. We find that the ion and electron temperatures are separated through shocks. Since the ion entropy is increased by energy dissipation at shocks and the Coulomb collisions are inefficient, electron temperature becomes about 10 times lower than the ion temperature in the hotspot ahead of the jet terminal shock. In the cocoon, electron temperature decreases by gas mixing between high temperature cocoon gas and low temperature shocked-ambient gas even when we neglect radiative cooling, but electrons can be heated through collisions with ions. Radiation intensity maps are produced by post processing numerical results. Distributions of the thermal bremsstrahlung radiation computed from electron temperature have bright filament and cavity around the jet terminal shock.

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25

Rozyczka, M., and A. Schwarzenberg-Czerny. "Hot Stripes Rather than Hot Spots in Cataclysmic Binaries: 2 - D Hydrodynamic Models." International Astronomical Union Colloquium 93 (1987): 377. http://dx.doi.org/10.1017/s0252921100105111.

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AbstractTwo-dimensional hydrodynamic models of the collision region between the stream and the disk in a cataclysmic binary are presented. The adiabatic collision results in significant mass loss from the system and produces large turbulent regions in outer parts of the disk. Radiative cooling of the collision region leeds to a semi-continuous injection of mass into the disk in the form of dense blobs of gas. In both cases the hot regions obtained as a result of the collision are over 1/6 of the circumference of the disk long and almost 40% of its radius deep, deserving to be renamed ‘hot stripes’.

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26

Russell, Christopher M. P., Michael F. Corcoran, Atsuo T. Okazaki, Thomas I. Madura, and Stanley P. Owocki. "X-Ray modeling of η Carinae & WR 140 from SPH simulations." Proceedings of the International Astronomical Union 6, S272 (July 2010): 630–31. http://dx.doi.org/10.1017/s1743921311011641.

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AbstractThe colliding wind binary (CWB) systems η Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these RXTE X-ray light curves, we apply 3D hydrodynamic simulations of the wind-wind collision using smoothed particle hydrodynamics (SPH). We find adiabatic simulations that account for the absorption of X-rays from an assumed point source of X-ray emission at the apex of the wind-collision shock cone can closely match the RXTE light curves of both η Car and WR140. This point-source model can also explain the early recovery of η Car's X-ray light curve from the 2009.0 minimum by a factor of 2-4 reduction in the mass loss rate of η Car. Our more recent models account for the extended emission and absorption along the full wind-wind interaction shock front. For WR140, the computed X-ray light curves again match the RXTE observations quite well. But for η Car, a hot, post-periastron bubble leads to an emission level that does not match the extended X-ray minimum observed by RXTE. Initial results from incorporating radiative cooling and radiative forces via an anti-gravity approach into the SPH code are also discussed.

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27

de Lozar, Alberto, and Lukas Muessle. "Long-resident droplets at the stratocumulus top." Atmospheric Chemistry and Physics 16, no. 10 (May 30, 2016): 6563–76. http://dx.doi.org/10.5194/acp-16-6563-2016.

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Abstract. Turbulence models predict low droplet-collision rates in stratocumulus clouds, which should imply a narrow droplet size distribution and little rain. Contrary to this expectation, rain is often observed in stratocumuli. In this paper, we explore the hypothesis that some droplets can grow well above the average because small-scale turbulence allows them to reside at cloud top for a time longer than the convective-eddy time t*. Long-resident droplets can grow larger because condensation due to longwave radiative cooling, and collisions have more time to enhance droplet growth. We investigate the trajectories of 1 billion Lagrangian droplets in direct numerical simulations of a cloudy mixed-layer configuration that is based on observations from the flight 11 from the VERDI campaign. High resolution is employed to represent a well-developed turbulent state at cloud top. Only one-way coupling is considered. We observe that 70 % of the droplets spend less than 0.6t* at cloud top before leaving the cloud, while 15 % of the droplets remain at least 0.9t* at cloud top. In addition, 0.2 % of the droplets spend more than 2.5t* at cloud top and decouple from the large-scale convective eddies that brought them to the top, with the result that they become memoryless. Modeling collisions like a Poisson process leads to the conclusion that most rain droplets originate from those memoryless droplets. Furthermore, most long-resident droplets accumulate at the downdraft regions of the flow, which could be related to the closed-cell stratocumulus pattern. Finally, we see that condensation due to longwave radiative cooling considerably broadens the cloud-top droplet size distribution: 6.5 % of the droplets double their mass due to radiation in their time at cloud top. This simulated droplet size distribution matches the flight measurements, confirming that condensation due to longwave radiation can be an important mechanism for broadening the droplet size distribution in radiatively driven stratocumuli.

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Inal, M. K., and M. S. Bentotoche. "Collisional-radiative calculations for the 3p1S0→ 3s3P1lasing line of neonlike germanium under anisotropic collision conditions." Journal of Physics: Conference Series 635, no. 5 (September 7, 2015): 052031. http://dx.doi.org/10.1088/1742-6596/635/5/052031.

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29

Smirnov, B. M. "Collision and radiative processes in emission of atmospheric carbon dioxide." Journal of Physics D: Applied Physics 51, no. 21 (May 2, 2018): 214004. http://dx.doi.org/10.1088/1361-6463/aabac6.

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30

Thomé, L., S. Moll, A. Debelle, F. Garrido, G. Sattonnay, and J. Jagielski. "Radiation Effects in Nuclear Ceramics." Advances in Materials Science and Engineering 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/905474.

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Due to outstanding physicochemical properties, ceramics are key engineering materials in many industrial domains. The evaluation of the damage created in ceramics employed in radiative media is a challenging problem for electronic, space, and nuclear industries. In this latter field, ceramics can be used as immobilization forms for radioactive wastes, inert fuel matrices for actinide transmutation, cladding materials for gas-cooled fission reactors, and structural components for fusion reactors. Information on the radiation stability of nuclear materials may be obtained by simulating the different types of interactions involved during the slowing down of energetic particles with ion beams delivered by various types of accelerators. This paper presents a review of the radiation effects occurring in nuclear ceramics, with an emphasis on recent results concerning the damage accumulation processes. Energetic ions in the KeV-GeV range are used to explore the nuclear collision (at low energy) and electronic excitation (at high energy) regimes. The recovery by electronic excitation of the damage created by ballistic collisions (SHIBIEC process) is also addressed.

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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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32

Barekzai, Mares, and Bernhard Mayer. "Broadening of the Cloud Droplet Size Distribution due to Thermal Radiative Cooling: Turbulent Parcel Simulations." Journal of the Atmospheric Sciences 77, no. 6 (May 21, 2020): 1993–2010. http://dx.doi.org/10.1175/jas-d-18-0349.1.

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Abstract Despite impressive advances in rain forecasts over the past decades, our understanding of rain formation on a microphysical scale is still poor. Droplet growth initially occurs through diffusion and, for sufficiently large radii, through the collision of droplets. However, there is no consensus on the mechanism to bridge the condensation coalescence bottleneck. We extend the analysis of prior methods by including radiatively enhanced diffusional growth (RAD) to a Markovian turbulence parameterization. This addition increases the diffusional growth efficiency by allowing for emission and absorption of thermal radiation. Specifically, we quantify an upper estimate for the radiative effect by focusing on droplets close to the cloud boundary. The strength of this simple model is that it determines growth-rate dependencies on a number of parameters, like updraft speed and the radiative effect, in a deterministic way. Realistic calculations with a cloud-resolving model are sensitive to parameter changes, which may cause completely different cloud realizations and thus it requires considerable computational power to obtain statistically significant results. The simulations suggest that the addition of radiative cooling can lead to a doubling of the droplet size standard deviation. However, the magnitude of the increase depends strongly on the broadening established by turbulence, due to an increase in the maximum droplet size, which accelerates the production of drizzle. Furthermore, the broadening caused by the combination of turbulence and thermal radiation is largest for small updrafts and the impact of radiation increases with time until it becomes dominant for slow synoptic updrafts.

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33

Liang Teng, Ma Kun, Chen Xi, Xie Lu-You, Dong Chen-Zhong, Shao Cao-Jie, Yu De-Yang, and Cai Xiao-Hong. "Theoretical study on radiative electron capture and subsequent radiative decay in collision of Xe54+ with Xe." Acta Physica Sinica 64, no. 15 (2015): 153401. http://dx.doi.org/10.7498/aps.64.153401.

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34

van Marle, Allard Jan, and Rony Keppens. "Numerical simulations of the circumstellar medium of massive binaries." Proceedings of the International Astronomical Union 6, S271 (June 2010): 405–6. http://dx.doi.org/10.1017/s1743921311018011.

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AbstractWe have made 3-D models of the collision of binary star winds and followed their interaction over multiple orbits. This allows us to explore how the wind-wind interaction shapes the circumstellar environment. Specifically, we can model the highly radiative shock that occurs where the winds collide. We find that the shell that is created at the collision front between the two winds can be highly unstable, depending on the characteristics of the stellar winds.

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35

Walder, Rolf, and Doris Folini. "Instabilities in colliding winds." Symposium - International Astronomical Union 163 (1995): 525–26. http://dx.doi.org/10.1017/s0074180900202623.

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The significance of radiative cooling for the stability properties of colliding astrophysical flows is shown. In the cases of WR ring nebula NGC 6888 and WR binary V444 Cyg it is found that thermal instabilities in the radiative loss function A(T) Tβ, β = β(T) not only have an influence on the dynamics of the collision zone, but also that they lead to a quasi-periodic increase of the radiated energy.

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36

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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37

Malomed, Boris A. "Collision-induced radiative dynamics and kinetics of driven nonlinear Schrödinger solitons." Physical Review A 41, no. 8 (April 1, 1990): 4538–40. http://dx.doi.org/10.1103/physreva.41.4538.

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38

Mahdi, Jinan F. "Calculation of the total mass stopping power for electrons in some human body tissues in the energy range 0.01-1000 MeV." Iraqi Journal of Physics (IJP) 15, no. 34 (January 8, 2019): 72–80. http://dx.doi.org/10.30723/ijp.v15i34.122.

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The mass collision energy loss (dE/dX), the mass radiative energy loss (Srad/) and the total mass stopping power of electrons in the energy range of 0.01 MeV up to 1000 MeV has been calculated for Lung, Urea and Skin. The results of the present work for the mass collision stopping power of electrons in Lung, Urea and Skin are in excellent agreement with the standard results given by ESTAR program, where the maximum percentage error between the present calculated values and that of ESTAR program in Lung tissue, Urea and Skin tissue is 0.27%, 0.3% and 0.8% respectively. The mass radiative energy loss of electrons in the same energy range is also calculated using a modified equation, and the results are found to be in very good agreement with the standard published values. The employed modified equation used to calculate the mass radiative energy loss of electrons is valid in the energy range of electrons from 0.01 MeV up to 1000 MeV and gives accurate results. As the results of total stopping power calculation are concerned, they are found in excellent agreement with the published results, where the error is less than 1%.

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39

Williams, J. F., J. B. Wang, and C. J. Carter. "A Monte Carlo Study of Radiation Trapping Effects." Australian Journal of Physics 50, no. 3 (1997): 645. http://dx.doi.org/10.1071/p96099.

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A Monte Carlo simulation of radiative transfer in an atomic beam is carried out to investigate the effects of radiation trapping on electron–atom collision experiments. The collisionally excited atom is represented by a simple electric dipole, for which the emission intensity distribution is well known. The spatial distribution, frequency and free path of this and the sequential dipoles were determined by a computer random generator according to the probabilities given by quantum theory. By altering the atomic number density at the target site, the pressure dependence of the observed atomic lifetime, the angular intensity distribution and polarisation of the radiation field is studied.

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40

Khadri, F., A. Chefai, and K. Hammami. "Low-temperature rate constants and radiative transfer for rotational de-excitation of C5S by collision with He." Monthly Notices of the Royal Astronomical Society 498, no. 4 (September 10, 2020): 5159–65. http://dx.doi.org/10.1093/mnras/staa2746.

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ABSTRACT The C5S molecule is the largest member of the series of sulphur-containing carbon chains CnS observed in space. Given the lack of data concerning this molecule, we computed rate coefficients of C5S(1Σ+) induced by collision with He. These rates are obtained for thermal temperature below 100 K by mean of a new two-dimensional potential energy surface (PES) calculated with the explicit correlated coupled cluster with single, double, and pertubative triple excitation (ccsd(t)-f12) ab initio approach and the aug-cc-pVTZ basis sets. The C5S–He PES presents three minimums of −59.726, −55.355, and −36.506 cm−1 below its dissociation limit. Using this PES, the integral cross-sections are performed in the close-coupling (CC) and coupled-state (CS) quantum time independent formalisms for $E_\mathrm{ c}\le 500 \, \mathrm{ cm}^{-1}$ and J ≤ 13 (for CC) and J ≤ 50 (for CS). By averaging these cross-sections we obtained the downward rate coefficients. The new collisional data are used to simulate the excitation of C5S in the circumstellar gas. We obtain the excitation and brightness temperatures of the four lines observed towards the IRC+10216 which confirms the necessity of using radiative transfer calculations to accurately determine C5S abundance since the local thermodynamic equilibrium conditions are not fulfilled. The new collisional data should help to estimate the abundance of C5S in several interstellar regions.

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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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42

Voitkiv, A. B., and N. Grün. "Radiative electron capture as a collision-stimulated transition between electron states dressed by the radiation field." Journal of Physics B: Atomic, Molecular and Optical Physics 34, no. 3 (January 18, 2001): 321–30. http://dx.doi.org/10.1088/0953-4075/34/3/309.

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43

Plašil, Radek, Illia Zymak, Pavol Jusko, Dmytro Mulin, Dieter Gerlich, and Juraj Glosík. "Stabilization of H + –H 2 collision complexes between 11 and 28K." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1978 (November 13, 2012): 5066–73. http://dx.doi.org/10.1098/rsta.2012.0098.

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Formation of via association of H + with H 2 has been studied at low temperatures using a 22-pole radiofrequency trap. Operating at hydrogen number densities from 10 11 to 10 14 cm −3 , the contributions of radiative, k r , and ternary, k 3 , association have been extracted from the measured apparent binary rate coefficients, k *= k r + k 3 [H 2 ]. Surprisingly, k 3 is constant between 11 and 22 K, (2.6±0.8)×10 −29 cm 6 s −1 , while radiative association decreases from k r (11 K)=(1.6±0.3)×10 −16 cm 3 s −1 to k r (28 K)=(5±2)×10 −17 cm 3 s −1 . These results are in conflict with simple association models in which formation and stabilization of the complex are treated separately. Tentative explanations are based on the fact that, at low temperatures, only few partial waves contribute to the formation of the collision complex and that ternary association with H 2 may be quite inefficient because of the ‘shared proton’ structure of .

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44

Kurilenkov, Yu K., and H. M. Van Horn. "On Radiative Transfer Near the Plasma Frequency at Strong Coupling." International Astronomical Union Colloquium 147 (1994): 581–85. http://dx.doi.org/10.1017/s0252921100026646.

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AbstractThe effects of strong coupling on the frequency-averaged optical characteristics of plasmas, such as the Rosseland mean-free-path, are considered. The general expression for the Rosseland mean opacity has been analyzed in terms of the transverse dielectric function of a dense plasma and the frequency-dependent effective collision frequency. The corresponding values of the absorption coefficient and the refractive index for a dense plasma are presented at ω ≤ ωp up in obvious forms.

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Conroy, Andrew, Catherine Ramsbottom, Connor Ballance, and Francis Keenan. "Towards the Provision of Accurate Atomic Data for Neutral Iron." Galaxies 6, no. 3 (August 25, 2018): 91. http://dx.doi.org/10.3390/galaxies6030091.

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The rich emission and absorption line spectra of Fe I may be used to extract crucial information on astrophysical plasmas, such as stellar metallicities. There is currently a lack, in quality and quantity, of accurate level-resolved effective electron-impact collision strengths and oscillator strengths for radiative transitions. Here, we discuss the challenges in obtaining an accurate model of the neutral iron atom and compare our theoretical fine-structure energy levels with observation for several increasingly large models. Radiative data is presented for several transitions for which the atomic data is accurately known.

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46

Guillot, T., D. Gautier, and G. Chabrier. "Molecular Opacities: Application to the Giant Planets." International Astronomical Union Colloquium 147 (1994): 576–80. http://dx.doi.org/10.1017/s0252921100026634.

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AbstractPresent available interior models of giant planets assume that the internal transport of energy is entirely convective and, accordingly, rule out any possibility of radiative transport. New opacity calculations at temperatures and densities occurring within the giant planets, taking into account H2-H2 and H2-He collision-induced absorption as well as infrared and visible absorption due to hydrogen, water, methane and ammonia are presented. These opacities are not high enough to exclude the presence of a. radiative zone in the molecular H2 envelope of Jupiter, Saturn and Uranus.

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47

Minaev, Boris F., Vitalina V. Kukueva, and Hans Ågren. "Configuration interaction study of the O2–C2H4exciplex: collision-induced probabilities of spin-forbidden radiative and non-radiative transitions." J. Chem. Soc., Faraday Trans. 90, no. 11 (1994): 1479–86. http://dx.doi.org/10.1039/ft9949001479.

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48

Morisset, Christophe, Valentina Luridiana, Jorge García-Rojas, Verónica Gómez-Llanos, Manuel Bautista, and Claudio Mendoza. "Atomic Data Assessment with PyNeb." Atoms 8, no. 4 (October 4, 2020): 66. http://dx.doi.org/10.3390/atoms8040066.

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PyNeb is a Python package widely used to model emission lines in gaseous nebulae. We take advantage of its object-oriented architecture, class methods, and historical atomic database to structure a practical environment for atomic data assessment. Our aim is to reduce the uncertainties in the parameter space (line ratio diagnostics, electron density and temperature, and ionic abundances) arising from the underlying atomic data by critically selecting the PyNeb default datasets. We evaluate the questioned radiative-rate accuracy of the collisionally excited forbidden lines of the N- and P-like ions (O ii, Ne iv, S ii, Cl iii, and Ar iv), which are used as density diagnostics. With the aid of observed line ratios in the dense NGC 7027 planetary nebula and careful data analysis, we arrive at emissivity ratio uncertainties from the radiative rates within 10%, a considerable improvement over a previously predicted 50%. We also examine the accuracy of an extensive dataset of electron-impact effective collision strengths for the carbon isoelectronic sequence recently published. By estimating the impact of the new data on the pivotal [N ii] and [O iii] temperature diagnostics and by benchmarking the collision strength with a measured resonance position, we question their usefulness in nebular modeling. We confirm that the effective-collision-strength scatter of selected datasets for these two ions does not lead to uncertainties in the temperature diagnostics larger than 10%.

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Elabidi, Haykel, Nébil Ben Nessib, and Sylvie Sahal-Bréchot. "Radiative atomic data and fine-structure collision strengths for neon-like sulfur." Journal of Physics: Conference Series 388, no. 6 (November 5, 2012): 062006. http://dx.doi.org/10.1088/1742-6596/388/6/062006.

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50

Aggarwal, K. M., F. P. Keenan, and A. Z. Msezane. "Energy Levels, Radiative Rates, and Collision Strengths for Transitions in Fe xvii." Astrophysical Journal Supplement Series 144, no. 1 (January 2003): 169–210. http://dx.doi.org/10.1086/344050.

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