Role of vibrational dynamics in electronic transitions in an intense laser field

PHYS 463

Patrick J. Nichols, pnichols@chem.und.edu and Mark R. Hoffmann, mhoffmann@chem.und.edu. Department of Chemistry, University of North Dakota, 236 Abbott Hall, Grand Forks, ND 98202
Theoretical descriptions of electronic transitions in electromagnetic fields normally assume that the lowest perturbation order Franck-Condon approximation is valid. However, it can not be expected to be useful in interactions in which the nuclei have significant momentum and/or the radiation field is intense. This work suggests a viable alternative to the traditional lowest order Franck-Condon approximation that is applicable to both conventional situations and the aforementioned regimes. Specifically, by considering an electronic-vibrational tensor product basis, and describing the nuclear wavefunctions in a the basis of eigenstates of nuclear momentum, it is possible to ensure the conservation of momentum without imposing unnecessary, and unphysical, constraints. The approach is independent of the description of the optical transition, and can be applied within e.g. time-dependent perturbation theory, Floquet theory and wavepacket propagation. The method is also equally applicable to bound states and dissociative potential energy states. We demonstrate the applicability of the approach on a study of the lowest six (field-free) electronic potential energy states Li2+ in an intense field. It is found that the inclusion of nuclear dynamics significantly changes the predicted spectra.
 

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006