Microwave spectroscopy of high-L,n=9Rydberg levels of nickel: Polarizabilities and moments of the Ni+ion

Abstract

The complete pattern of Rydberg binding energies of the 18 $n=9$ levels of nickel with $L=6$, 7, and 8 was measured using microwave plus resonant-excitation Stark-ionization spectroscopy. The measured pattern is consistent with the form predicted with the effective potential model, showing significant structure proportional to scalar products of tensor operators of order 0--4. The variation of the structure with $L$ separates the various contributing terms and provides determinations of several properties of the Ni${}^{+}$ core ion. These include the quadrupole moment, $Q$ $=$ \ensuremath{-}0.469 78(9) a.u., the hexadecapole moment, \ensuremath{\Pi} $=$ 0.36(5) a.u., the scalar and tensor dipole polarizabilities, ${\ensuremath{\alpha}}_{D,0}=$ 7.949(2) a.u., ${\ensuremath{\alpha}}_{D,2}=0.905$(12) a.u., the scalar quadrupole polarizability, ${\ensuremath{\alpha}}_{Q,0}=55$(8) a.u., the $g$ value, ${g}_{J}=1.257$(14), and the vector hyperpolarizability, ${\ensuremath{\beta}}_{D,1}=0.454$(24) a.u.