Pulse-width and isotope effects in femtosecond-pulse strong-field dissociation of H-2(+) and D-2(+) - art. no. 063402

Using a high-resolution setup, we investigate the fragmentation of H-2 and D-2 in intense 790 nm laser pulses with pulse widths of 28 fs and 80 fs. Th e measured H+ (D+) kinetic energies resulting from effective two-photon dis sociation of H-2(+) (D-2(+)) show a clear dependence on the pulse width and on the isotope. One-dimensional calculations reproduce these effects and s how that they mainly originate from the H-2(+) (D-2(+)) dissociation dynami cs. Further, we find that the initial ionic state before dissociation is no t simply given as a Franck-Condon distribution over unperturbed ionic state s. Rather it is a complex mixture of initial wave packets (covering, howeve r, a small energy range) created by multiphoton ionization of H-2 and D-2 a t various rimes during the action of the pulse.