Decrease in imprisonment of resonance radiation due to the broadening of the absorption line contour caused by the rotation of the plasma sphere

Abstract

Imprisonment of resonance radiation in the spherical barium plasma rotating around its symmetry axis is numerically studied. Photoexcitation of barium ions at resonance transition with the wavelength λ0= 455.4 nm by laser radiation is modeled. A numerical algorithm allows one to calculate the emission spectrum and the Holstein's escape factor of resonant radiation using the afterglow intensity of rotating plasma. The full width at half maximum of the emission line is considerably wider than the one for the static medium, and the central frequency of emission is shifted to either red or blue wing of the spectrum. Location of the frequency of intensity maximum of the emission line unambiguously determines the projection of velocity of ions on the ray direction in the plasma. For rotational plasma, the imprisonment of resonant quanta decreases due to the broadening of the ion absorption line. The appearance of two qualitatively novel effects that distinguish rotating plasma from static one is predicted: 1) more facilitated diffusion of resonant photons to the medium surface and more facilitated escape of them out of it (effect strengthened escape); 2) presence of a velocity gradient along the sphere radius leads to “spreading” of the line over a wider frequency range, impeding free propagation of continual photons (effect of frequency band narrowing).