Enhancement of narrow resonances in photoabsorption from the He atom in metastable states

Abstract

Photoionization cross sections from metastable (1s2s) 1Se, 3Se states of He atom, for photon energies below the He+ (N=2) threshold are calculated using the hyperspherical close-coupling (HSCC) method. The results are compared with photoionization cross sections from the ground state He atom. By convoluting the calculated spectra with a resolution of 5.4 meV, the authors show that the narrow doubly excited states, which are weakly populated by photoabsorption from the ground state, are populated prominently in photoabsorption from the metastable (1s2s) 1Se state. The 3P0 doubly excited states populated from the photoabsorption of metastable (1s2s) 3Se state are also studied.