Cascade Anticrossing Measurement of the Anomalous Hyperfine Structure of the4D2State of Rubidium

Abstract

A new technique, cascade anticrossing spectroscopy, has been developed to determine the effective values of $〈{r}^{\ensuremath{-}3}〉$ for the spin-dipole, orbital, contact, and quadrupole hyperfine interaction terms for the $4^{2}D$ state of Rb. They are, in units of ${10}^{24}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, ${〈{r}^{\ensuremath{-}3}〉}_{d}=\ensuremath{-}0.36(8)$, ${〈{r}^{\ensuremath{-}3}〉}_{l}=+0.20(2)$, ${〈{r}^{\ensuremath{-}3}〉}_{c}=\ensuremath{-}4.3(1)$, and ${〈{r}^{\ensuremath{-}3}〉}_{q}=+0.79(66)$, respectively. The negative value of ${〈{r}^{\ensuremath{-}3}〉}_{d}$ and the unexpectedly large value of ${〈{r}^{\ensuremath{-}3}〉}_{c}$ are surprising. The fine-structure splitting has been measured to be - 13 360.9(8) MHz.