Hyperfine quenching of $(3d^94s)\, ^3$D$_3$ states in Ni-like ions

We study quenching of decays from metastable ($3d^9\,4s$) $^3$D$_3$ states of Ni-like ions with odd-A nuclei caused by hyperfine mixing with nearby $^{1,3}$D$_2$ states. A detailed discussion is given for the Ni-like ions $^{132}$Xe, $^{131}$Xe, and $^{129}$Xe. For $^{132}$Xe ($I$=0) the $^3$D$_3$ state decays by M3 emission. For the odd-A nuclei $^{131}$Xe ($I$=3/2) and $^{129}$Xe ($I$=1/2), each hyperfine level decays at a separate rate owing to hyperfine mixing. Comparisons are made with other calculations [1] and with experiment [2] for the the three isotopes of Ni-like Xe. Decay rates of the hyperfine levels of $^3$D$_3$ states are evaluated for isotopes of those Ni-like ions in the range $^{77}$Se$^{8+}$ -- $^{207} $Pb$^{54+}$ that have nuclear spin $I$=1/2 using relativistic many-body perturbation theory.\vspace{0.25pc} \noindent [1]\ K. Yao, M. Andersson, T. Brage, R. Hutton, P. J\"{o}nsson, and Y. Zou, Phys.\ Rev.\ Lett.\ {\bf 98}, 269903 (2007). \noindent[2]\ E. Tr\"{a}bert, P. Beiersdorfer, and G. V. Brown, Phys.\ Rev.\ Lett.\ {\bf 98}, 263001 (2007).