Competition between multi-photon emission of the 1s and the 2s electron from He 1s2s 1S

Abstract

Using the R-matrix Floquet approach, we have investigated multiphoton ionization of the 1s2s 1S state of He. We compare emission rates for the 1s and 2s electrons after absorption of N photons, where N is the minimum number of photons needed to emit the 1s electron. For N = 1 and 2, we find that emission of the 1s electron dominates, while for N = 4 emission of the 2s electron dominates. For N = 3, both processes are of comparable magnitude. In the absence of resonances, emission of the 1s electron typically becomes less likely by a factor of 5 for each additional photon absorbed. However, for N = 4, emission of the 1s electron is strongly enhanced due to the intermediate 2s2p 1P resonance.