Absolute photoionization cross-section measurements of the Kr I isoelectronic sequence

Abstract

Photoionization spectra have been recorded in the $4s$, $4p$, and $3d$ resonance regions for the Kr I isoelectronic sequence using both the dual laser produced plasma (DLP) technique (at DCU) to produce photoabsorption spectra, and the merged ion beam and synchrotron radiation technique (at ASTRID) to measure absolute photoionization cross sections. Profile parameters are compared for the $4s\text{\ensuremath{-}}np$ resonances of ${\mathrm{Rb}}^{+}$ and ${\mathrm{Sr}}^{2+}$. Many $4p\ensuremath{\rightarrow}ns$, $md$ transitions are identified with the aid of Hartree-Fock calculations, and consistent quantum defects are observed for the various $ns$ and $md$ Rydberg series. Absolute single and double photoionization cross sections recorded in the $3d$ region for ${\mathrm{Rb}}^{+}$ and ${\mathrm{Sr}}^{2+}$ ions show preferential decay via double photoionization. This is only the second report to our knowledge where both the DLP technique and the merged-beam technique have been used simultaneously to record photoionization spectra, and the advantages of both techniques (i.e., better resolution in the case of DLP and values for absolute photoionization cross sections in the case of the merged-beam technique) are highlighted.