Photodissociation of H₂⁺ and HD⁺ in an intense laser field

The photodissociation of H₂⁺ and HD⁺ by an intense laser pulse is investigated by solving the close-coupling equations without discretization. For the case of H₂⁺ the photodissociation spectra are calculated under the condition mimicking the experimental one, and a fairly good agreement with the experiment is obtained. The uncertainty in the relative phases of initial states is found to lead to somewhat smoothing of the spectra, depending on the pulse length. It is also found that Raman-type transitions via intermediate dissociation continuum play an important role in determining the photodissociation spectra. This leads to a population increase of lower vibrational states and deforms the spectral profile. Dissociation from the lower vibrational states due to the bond softening is not strong enough. Photodissociation spectra and angular distribution are calculated also for HD⁺ under the same conditions as in the H₂⁺ case. The dipole transitions lead to additional structures in the energy spectra and angular distribution. There is a noticeable difference in the peak positions of dissociation spectrum for particles dissociated by the direct electronic-dipole transition and by the transitions via intermediate bound states. The photodissociation dynamics is further clarified by using the three-dimensional plots of the spectra as a function of the field intensity and frequency.