Core polarizability of rubidium using spectroscopy of the ng to nh, ni Rydberg transitions

Abstract

We present a precise measurement of the rubidium ionic core polarizability. The results can be useful for interpreting experiments such as parity violation or black-body radiation shifts in atomic clocks since the ionic core electrons contribute significantly to the total electrical polarizability of rubidium. We report a dipole polarizability $\alpha_d$ = $9.116 \pm 0.009$ $a_0^3$ and quadrupole polarizability $\alpha_q$ = $38.4 \pm 0.6$ $a_{0}^{5}$ derived from microwave and radio-frequency spectroscopy measurements of Rydberg states with large angular momentum. By using a relatively low principal quantum number ($17 \leq n \leq 19$) and high angular momentum ($4 \leq \ell \leq 6$), systematic effects are reduced compared to previous experiments. We develop an empirical approach to account for non-adiabatic corrections to the polarizability model. The corrections have less than a 1\% effect on $\alpha_d$ but almost double $\alpha_q$ from its adiabatic value, bringing it into much better agreement with theoretical values.