Calculation of electron-impact excitation from metastable states of the Sr atom

Abstract

Electron-impact excitation of Sr from metastable states is studied in the framework of an elaborate close-coupling approximation, using accurate target wave functions. An interpretation is given of measured cross sections, including their near-threshold resonance structure. The cross sections for transitions induced from the 5s5p{sup 3}P metastable level to the 5s5d{sup 3}D, 5p{sup 23}P, 5s6s{sup 3}S, 4d5p{sup 1}D, 5s4f{sup 3}F, 4d5p{sup 3}F, and 5s6p{sup 3}P levels are calculated in Born-Ochkur and two-state and six-state close-coupling approximations. We also consider transitions from the 5s{sup 21}S ground state to these levels. The calculations are based on a nonrelativistic Hamiltonian. In the configuration-interaction approximation, accurate wave functions are used for the outer electrons, with a frozen core. The results are found to be in good agreement with the most recent experimental data. {copyright} {ital 1997} {ital The American Physical Society}