Simultaneous electron-photon excitation of helium in an Nd:YAG laser field

Kevin M. Dunseath (1) , Mariko Dunseath-Terao (1)

1 IPR - Institut de Physique de Rennes

R-matrix Floquet theory is used to study the laser-assisted electron-impact excitation of helium at collision energies close to the He(1s2 ) thresholds in the presence of a Nd:YAG laser field of intensity 1010 W cm−2. A strong ac Stark mixing occurs between the 1s2s 3S and 1s2p 3Po states. The He−(1s2s2 2S) resonance gives rise to a series of structures in the integrated cross sections, in particular a dominant peak below the first excitation threshold. Agreement with experiment is very good at low energies, but at higher energies, the calculated signal remains small while the experimental results are very negative. The role of multiphoton ionization of the metastable states by the Nd:YAG laser field as a mechanism for signal loss in the experiment is also investigated.

Domaines: Physique Atomique [physics.atom-ph]

Kevin M. Dunseath, Mariko Dunseath-Terao. Simultaneous electron-photon excitation of helium in an Nd:YAG laser field. Journal of Physics B: Atomic, Molecular and Optical Physics, 2013, 46 (23), pp.235201. ⟨10.1088/0953-4075/46/23/235201⟩. ⟨hal-00905582⟩