Laser-probing measurements and calculations of lifetimes of the5dD3∕22and5dD5∕22metastable levels inBaII

Abstract

The two metastable levels $5d\phantom{\rule{0.2em}{0ex}}^{2}D_{3∕2}$ and $5d\phantom{\rule{0.2em}{0ex}}^{2}D_{5∕2}$ in $\mathrm{Ba}\phantom{\rule{0.2em}{0ex}}II$ both show extremely long lifetimes of the order of several tens of seconds each. This has been found both by experiments and by theoretical predictions. The small transition probabilities associated with these two levels make them interesting and challenging for theoreticians as well as for experimentalists. Several calculations and measurements of these two lifetimes have been made previously but discrepancies between the results are present. This article presents values of $\ensuremath{\tau}=89.4\ifmmode\pm\else\textpm\fi{}15.6\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ for the $^{2}D_{3∕2}$ level and $\ensuremath{\tau}=32.0\ifmmode\pm\else\textpm\fi{}4.6\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ for the $^{2}D_{5∕2}$ level measured in a beam-laser experiment performed at the ion storage ring CRYRING. These values are supported by our new calculations resulting in $\ensuremath{\tau}=82.0\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ for the $^{2}D_{3∕2}$ level and $\ensuremath{\tau}=31.6\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ for the $^{2}D_{5∕2}$ level.