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

K M Dunseath, M Terao-Dunseath
2013 Journal of Physics B: Atomic, Molecular and Optical Physics  
R-matrix Floquet theory is used to study laser-assisted electron-impact excitation of helium at collision energies close to the He(1s2ℓ) thresholds, in the presence of a Nd:YAG laser field of intensity 10 10 W cm −2 . Strong AC Stark mixing occurs between the 1s2s 3 S and 1s2p 3 P o states. The He − (1s2s 2 2 S) 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
more » ... periment 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.
doi:10.1088/0953-4075/46/23/235201 fatcat:avm2ulhkybeehnarnabtsiponq