L-dependences in the autoionization of high-n Rydberg states

A comparative study of the autoionization of high-n, 120 ≤ n ≤ 160, strontium Rydberg atoms with intermediate values of L, 0 ≤ L ≤ 5, following excitation of the 5s ²S_1/2 → 5p ²P_1/2 transition in the core ion is presented. Measurements of Rydberg atom loss as the core ion-exciting laser frequency is scanned are used to determine the widths, i.e., lifetimes, of the two-electron-excited states together with the shift of the core ion resonance frequency from that of the bare core ion. The data demonstrate that, for a fixed value of L, both the widths of the autoionization loss features and their detunings vary as 1/(n−δ)³, where δ is the quantum defect, i.e., depend on the probability of finding the Rydberg electron in the vicinity of the core ion. For a fixed value of n, however, no simple L-dependence of either of these quantities is seen. The experimental results are discussed from the standpoint of quantum defect theory as well as using a two-active-electron model.