https://doi.org/10.1140/epjd/e2010-00209-2
Multiphoton effects in laser-assisted ionization of a helium atom by electron impact
Department of Theoretical Physics, Indian association for the Cultivation of Science, Jadavpur, Kokata, 700032, India
Corresponding author: a chand_sin@hotmail.com
Received:
21
May
2010
Revised:
24
June
2010
Published online:
6
August
2010
The dynamics of the electron impact multiphoton ionization of a He atom in
the presence of an intense laser field (n
, 2e) is studied
theoretically for laser polarization (
) and perpendicular
(
) to the incident momentum. The triple differential (TDCS) as well
as the double differential (DDCS) cross sections are studied for the
coplanar asymmetric geometry. The results are compared with the only
available kinematically complete experiment at high incident energy (1000 eV). Significant laser modification (enhancement) is noted due to
multiphoton effects in the present binary and recoil peak intensities of the
TDCS for both the geometries, in qualitative agreement with the experiment.
In the single photon case, the net effect of the laser field is to suppress
the field free (FF) TDCS as well as the DDCS in the zeroth order
approximation of the ejected electron wave function (CV), while in the first
order (MCV), the cross sections are found to be enhanced. The CV multiphoton
cross sections obey the famous Kroll Watson (KW) sum rule while the latter
does not hold good in the corresponding MCV approximation.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2010
