Analysis of extreme ultraviolet spectra of laser-produced Cd plasmas*

Abstract

In order to provide detailed information about Cd structure and gain more insight regarding ionization degrees and types of transition, as well as the understanding of the temporal evolution behavior of laser produced Cd plasmas, extreme ultraviolet spectra of laser-produced cadmium (Cd) plasmas have been measured in the 8.4–12 nm region using spatio-temporally resolved laser-produced plasma spectroscopy technique. Spectral features were analyzed by the Hartree–Fock (HF) method with relativistic correlations (HFR) using the Cowan code. The results showed that the 4p–5s resonance transition arrays from Cd9+ to Cd13+ merged to form intense lines in this spectral region. A number of new spectral features from Cd9+ and Cd10+ ions are reported in this study. Based on the assumption of a normalized Boltzmann distribution among the excited states associated with a steady-state collisional–radiative model, the plasma parameters were obtained by comparing the experimental and simulated spectra. As a result, we succeeded in reproducing the synthetic spectra for different time delays, which yielded good agreement with the experiments. The temporal evolution behaviors of electron temperature and electron density of plasma were also analyzed.