Electron-atom ionisation in a resonant electromagnetic field

Abstract

Electron-atom ionisation in the presence of a resonant EM field is considered theoretically, taking the hydrogen atom as an example. The radiation field is taken to have a frequency matching the 1s-2p transition frequency. The theoretical treatment is based on the Coulomb-Born wave approximation and on the two-level atom model. The physical picture arising from the resulting field-assisted triple differential cross section (TDC) is that of ionisation events taking place simultaneously from the ground and the excited 2p states, the role of the radiation field being mainly that of pumping target atoms.