Determination of the parameters of the active medium of a recombination laser utilizing transitions in the BeIV ion

An investigation was made of the formation of the active medium of a recombination laser utilizing the 4f–5g transition in the BeIV ion in an expanding laser plasma formed from a solid-state target. Spectroscopic methods were used to determine the electron density and temperature in the lasing zone. These parameters were used to find the gain due to the 4f–5g transition in the BeIV ion: at distances $x\gtrsim0{.}4$ cm from the target the gain was $5\cdot10^{-2}-10^{-1}$ cm$^{-2}$. These values were close to the gain deduced experimentally from the threshold characteristics of the lasing process.