Asymmetric repumping of the Lyman-alpha components of hydrogen-like ions in a dense expanding plasma

Abstract

Lyman-alpha lines from H-like iron excited in the hot and dense micropinch plasma of low inductance vacuum sparks demonstrate a strong deviation from the statistical value of 0.5 of the line intensity ratio I(2p 2P 1 2 -1s 2S 1 2)I(2p 2P 3 2 -1s 2S 1 2) . A mechanism of intensity repumping based on a photon frequency shift in the expanding plasma is proposed. Numerical Monte-Carlo simulations for the radiation transport of the Lyman-alpha photons show that at reasonable plasma parameters for electron density, temperature, size and expansion velocity of a micropinch plasma in its final state of development, the spectrum can show an inverted line intensity ratio. The FWHM of the lines correlates mainly to motion broadening.