3d absorption spectra of Sr I through Sr IV.

Abstract

The extreme ultraviolet photoabsorption spectra of neutral to three-times-ionized strontium have been recorded in a comprehensive series of experiments with the dual laser-produced plasma technique. Striking differences were found in the spectra, which can be attributed to the transfer of oscillator strength from 3d\ensuremath{\rightarrow}np to 3d\ensuremath{\rightarrow}nf transitions at ${\mathrm{Sr}}^{2+}$ due to nf wave-function contraction. In Sr and ${\mathrm{Sr}}^{+}$, 3d\ensuremath{\rightarrow}5p transitions dominate; in ${\mathrm{Sr}}^{2+}$, 3d\ensuremath{\rightarrow}nf transitions are most intense, while in ${\mathrm{Sr}}^{3+}$ the 4p subshell opens and 3d\ensuremath{\rightarrow}4p transitions are the strongest features. Partial cross sections for 3d\ensuremath{\rightarrow}\ensuremath{\varepsilon}f and 3d\ensuremath{\rightarrow}\ensuremath{\varepsilon}p photoionization were calculated and compared with experiment.