Doppler shift and frequency redistribution function in the laboratory frame. Effect on the output of neon-like germanium x-ray lasers

This work is devoted to the effect of the Doppler shift and frequency redis tribution on the output of soft-x-ray lasers operating in the collisional e xcitation scheme. Owing to the Doppler frequency detuning, the lineshape fu nction as well as the redistribution function in the laboratory frame may d iffer from the same functions calculated in the atom frame. In fact, the la sing lines 0-1 (19.6 nm) and 2-1 (23.6 nm) in neon-like germanium show an i mportant Doppler broadening and the redistribution functions calculated in the two frames differ by a large amount. The emissivity, corrected in order to account for frequency redistribution, is calculated, and the radiative transfer equation is solved. We show that the intensities of the above line s depend on the frame chosen.