Properties of Ni$^{+}$ from spectroscopy of high-L Rydberg levels of Ni

A single high-L Rydberg electron bound to the $^{2}$D$_{5/2}$ ground state of Ni$^{+}$ leads to a Rydberg fine structure consisting of six levels for each value of L, corresponding to the six possible values of the quantum number K=L+J. The resulting fine structure pattern in n=9, L $>$ 4 levels of Ni was resolved in measurements of the Ni 9-19 and 9-20 transitions, using the Resonant Excitation Stark Ionization Spectroscopy technique [1]. The pattern was analyzed to determine the scalar and tensor polarizabilities and the permanent electric quadrupole moment of Ni$^{+}(^{2}$D$_{5/2})$. [1] E.L Snow, et. al. Phys. Rev. A 71, 022510 (2005)