Escape factors for Stark-broadened line profiles

Abstract

Escape factors for upper and lower limits to the source function appropriate for spherical geometry have been evaluated using a set of Stark-broadened line profiles, computed with different approximations, for the Ly-∝ line of Ar xviii. The method used to compute the escape factors, which is based on a general formalism, can be applied to any kind of line profile and is suitable for any geometry. The escape factor is expressed as an integral over the frequency of a functional of the line profile; hence our treatment highlights its dependence on the line profile. Comparisons are made with previous calculations that used Holtsmarkian line profiles and significant differences are noted. This work has been submitted for publication to J. Phys. B (London). This work was supported by the U.S. DOE Grant No. DEA508-833PP-40177.

Analysis of microscopic magnitudes of radiative blast waves launched in xenon clusters with collisional-radiative steady-state simulations

“…This modification circumvents the need to perform a simultaneous calculation of radiation transport and atomic physics. To compute the escape factors we have adopted the technique described in [66]. Thus, assuming a uniform distribution of emitting atoms and isotropic emission, for the three basic geometries-plane, cylindrical and spherical-the escape factor Aj¡ is written as…”

ZEST: A Fast Code for Simulating Zeeman-Stark Line-Shape Functions

“…In particular, our analysis took advantage of the strong influence of the Stark effect on the relative intensity between the structures at hν = 3266.8 eV and hν = 3271 eV, which correspond roughly to the position of the unperturbed lines 1s + 3p − → 1s 2 and 1s + 3p + → 1s 2 , respectively. As the electron density increases, the states in the complex (1s) 1 (3s3p3d) 1 are mixed together more efficiently, resulting in a progressive redistribution of strengths among the 4 The temperature T = 440 eV was taken from a more detailed analysis of the He-like and Li-like spectra using the non-LTE code DEDALE [10] and the present line-shape code ZEST (see Acknowledgments). lines.…”

“…These escape factors depend closely on line-shape profiles I ν , with integrals of the type dνI ν e −τ 0 I ν /I 0 where τ 0 is the optical depth at the center of the line. It is often important to include Stark broadening in the calculation of these factors, though it is not an easy task [4].…”

Argon K-shell and bound-free emission from OMEGA direct-drive implosion cores

“…Radiation transport effects in the atomic kinetics due to line trapping in the plasma are taken into account via escape factors [14], and the emergent line intensity distribution is computed using an analytical integration of the radiation transport equation for the case of a uniform, spherical plasma source [6[. On the one hand, the line shapes employed in the calculation of the escape factors included in the atomic kinetics are Voigt line profiles in which the width of the Lorentzian contribution considers natural and an approximate Stark width [15] and the width of the Gaussian contribution characterizes the thermal Doppler broadening.…”