Theoretical and experimental study of uv lasers in Be-like ions pumped by resonant photoexcitation

A uv laser based on resonant photoexcitation is described. This type of laser is a prototype for soft-x-ray lasers in isoelectronic analogs. Intense, Mn v i–line radiation at 310 Å from a ${\mathrm{CO}}_2$-laser-produced plasma was used to resonantly pump Ci i i ions, in an adjacent vacuum-arc discharge, from the 2$s^2$ ground state to the 2s4p upper level. Electron collisions rapidly redistribute the population of the pumped 4p level among other n=4 levels. Enhanced fluorescence coincident with the Mn v i–line radiation was observed on many 4-3 transitions in Ci i i. To describe the kinetics in C i i i ions, a 72-level collisional radiative model was constructed with up-to-date atomic data. Measured values of electron density and temperature in the C and Mn plasmas were used as inputs to the model. To verify this model, the populations of excited states in C i i i ions were measured spectroscopically and compared with predictions. Gain coefficients of about 0.1 ${\mathrm{cm}}^{\mathrm{-}1}$ were predicted by the model. These gains were found to be consistent with the experiments. Single-pass gain measurements showed that the total gain-length product was 0.5 in two C i i i lines at 2177 and 2163 Å. Laser action at these wavelengths was demonstrated in a resonant Fabry-Perot cavity. This C i i i–Mn v i photoexcitation scheme is a prototype for soft-x-ray lasers in higher Z, isoelectronic analogs, such as Mg i x–Al x i and others.