Potential barrier effects on double excitation series of Ca I and Sr I

Abstract

Observations of the series due to simultaneous excitation of two valence electrons to 4p ns , nd in Ca i and 5p ns , n d in Sr I are reported. The importance of the angular momentum barrier for the doubly excited n d series and, by comparison, for the n d series of singly excited even parity states is inferred with the help of single configuration Hartree-Fock calculations. This contrasts with the situation in Mg Ι, where wavefunction collapse does not occur in the doubly excited 3p n d series.