Autoionization of very-high-n strontium Rydberg states

We study, using a combination of experiment and theory, the excitation and decay of very-high-$n\phantom{\rule{4pt}{0ex}}(n\ensuremath{\sim}280\text{--}430)$ strontium autoionizing Rydberg states formed by near-resonant driving of the $5s\phantom{\rule{0.16em}{0ex}}^{2}S_{1/2}\ensuremath{\rightarrow}5p\phantom{\rule{0.16em}{0ex}}^{2}P_{1/2}$ core-ion transition. The branching ratio between decay through radiative transitions and through autoionization is explored. Autoionization rates are measured as a function of both the $n$ and $\ensuremath{\ell}$ quantum numbers of the Rydberg electron. The nonstationary decay dynamics is studied by creating and manipulating Rydberg wave packets and by varying the laser pulse that drives the core excitation.