Partial photoionization cross sections for Hg between 600 and 250 Å. Effect of spin-orbit coupling on theD522D322branching ratio of Hg

Abstract

By means of photoelectron spectroscopy, we have measured the branching ratios for production of the $^{2}S_{\frac{1}{2}}$, $^{2}D_{\frac{5}{2}}$, and $^{2}D_{\frac{3}{2}}$ states of ${\mathrm{Hg}}^{+}$ by photoionization of Hg in the wavelength range 600-250 \AA{}. These branching ratios are combined with earlier measurements of the total photoionization cross section to produce partial photoionization cross sections for the above processes. The wavelength dependence of the $^{2}D_{\frac{5}{2}}:^{2}D_{\frac{3}{2}}$ branching ratio exhibits a systematic deviation relative to the statistical value of 3:2. That is, this ratio is greater than statistical where the respective partial cross sections are increasing with photon energy and is less than statistical when the partial cross sections are decreasing. This effect was previously predicted and is a consequence of spin-orbit coupling in the ionized subshell, in this case, the $5d$ subshell of Hg.