A detailed theoretical and experimental investigation is presented of the excited-level population distribution in a Li-Ne vapor under excitation by a photoionization electron source. This source produces a subnanosecond burst of hot ($T_e$∼20 eV) electrons with a peak density in excess of 5×${10}^{15}$ ${\mathrm{cm}}^{\mathrm{-}3}$. The electrons are generated as a result of photoionization of Ne atoms by x rays emitted from a plasma produced by a 100-mJ laser pulse of 600 ps duration. Measurements of Li(1$s^2$2p)-atom density, and of electron density, have been performed with subnanosecond time resolution under various conditions of excitation. A comprehensive rate-equation model is described and its predictions are seen to be in good agreement with experiment. It is shown that the population distribution in the Li-Ne vapor is strongly influenced by recombination. Under the conditions of these experiments, rates for this process as high as 3×${10}^9$ ${\mathrm{s}}^{\mathrm{-}1}$ were observed.

• Received 8 April 1985

DOI:https://doi.org/10.1103/PhysRevA.33.2563