5p1/2nℓj autoionizing states of strontium for 0≤ℓ≤5

Abstract

We report a comprehensive experimental and theoretical study of the autoionization of core-excited $5{p}_{1/2}n{\ensuremath{\ell}}_{j}$ strontium Rydberg states for intermediate values of ${\ensuremath{\ell}}_{j}$ in the range $0\ensuremath{\lesssim}{\ensuremath{\ell}}_{j}\ensuremath{\lesssim}5$. For a given value of ${\ensuremath{\ell}}_{j}$ autoionization, which results from the energy exchange between the two excited valence electrons, is found to scale as $\ensuremath{\sim}1/{n}^{3}$, mirroring the decrease in the Rydberg electron probability density in the vicinity of the inner $5{p}_{1/2}$ electron cloud. In contrast, the ${\ensuremath{\ell}}_{j}$ dependence of the autoionization rate is more complex. For the larger values of ${\ensuremath{\ell}}_{j}$ $(\ensuremath{\ge}4)$, the autoionization rate decreases as ${\ensuremath{\ell}}_{j}^{\ensuremath{-}5}$ due to the centrifugal barrier, which prevents the Rydberg electron from penetrating the core and inner $5{p}_{1/2}$ electron cloud. For the low-${\ensuremath{\ell}}_{j}$ core-penetrating Rydberg states, the scattering phase shift induced by the effective core potential becomes important in determining both the autoionization rates, which no longer show a monotonic variation with ${\ensuremath{\ell}}_{j}$, and the quantum defects.