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 5p₁/₂nℓⱼ strontium Rydberg states for intermediate values of ℓⱼ in the range 0≲ℓⱼ≲5. For a given value of ℓⱼ autoionization, which results from the energy exchange between the two excited valence electrons, is found to scale as ∼1/n³, mirroring the decrease in the Rydberg electron probability density in the vicinity of the inner 5p₁/₂ electron cloud. In contrast, the ℓⱼ dependence of the autoionization rate is more complex. For the larger values of ℓⱼ (≥4), the autoionization rate decreases as ℓⱼ⁻⁵ due to the centrifugal barrier, which prevents the Rydberg electron from penetrating the core and inner 5p₁/₂ electron cloud. For the low-ℓⱼ 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 ℓⱼ, and the quantum defects.