A momentum-conserving Franck-Condon approximation: theory and application to the photodissociation of Li2+ in an intense laser field.
A new, computationally efficient approximation to calculating matrix elements between vibrational-electronic states that does not assume stationary nuclei is introduced. The approach emphasizes the importance of the conservation of nuclear momenta. The calculated quantities can be used wherever equivalent quantities from standard Franck-Condon treatments can be used. The new method is illustrated by a time-dependent perturbation theory description of the photodissociation of the Li(2) (+) molecular cation in an intense laser field (I=0.9x10(12) W/cm(2)), which was previously identified in a detailed study of the electronic structure [Khait et al., J. Chem. Phys. 122, 094111 (2005)] as likely to have unusual sensitivity to the initial vibrational state in dynamics. The current study confirms this speculation and shows this to be a specific instance of a situation in which nuclear dynamics during an electronic optical transition cannot be ignored.
Nichols
Patrick
P
Chemistry Department, University of North Dakota, Grand Forks, North Dakota 58202-9024, USA.
Hoffmann
Mark R
MR