Time-resolvedL-shell absorption spectroscopy: A direct measurement of density and temperature in a germanium laser-produced plasma

L-shell absorption of germanium transitions has been exploited for the first time to diagnose the low-temperature, high-density region of multilayered targets irradiated by 0.35-μm laser light at irradiances around ${10}^{14}$ W/${\mathrm{cm}}^2$. A detailed atomic-physics package has been used to relate the observed absorption wavelengths to the ionic distribution from Ge v i i to Ge x x and to the electron plasma parameters. Results show time-dependent temperature variations closely following the driving-laser pulse shape, in agreement with hydrocode simulations.