Laser-induced resonant structures in a close-coupling calculation of two-frequency multiphoton dissociation ofHD+

Abstract

A time-independent close-coupling calculation of multiphoton dissociation of ${\mathrm{HD}}^{+}$ from the ground vibrational level in two fields, each of intensity ${10}^{12}{\mathrm{W}/\mathrm{c}\mathrm{m}}^{2},$ and frequencies below the dissociation threshold, is presented. The lower frequency ${\ensuremath{\omega}}_{1}$ is varied around the difference between the energies of the Stark shifted $v=6$ and $v=0$ levels, while the higher frequency ${\ensuremath{\omega}}_{2}$ is varied by about 2000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ up to the dissociation threshold of the $v=0$ level. The dissociation linewidth of the initial $v=0$ level as a function of ${\ensuremath{\omega}}_{1}$ is a Lorentzian (as expected for a simple resonant two photon dissociation process) whose height, position, and width all depend upon the value of ${\ensuremath{\omega}}_{2}.$ With respect to ${\ensuremath{\omega}}_{2}$ this linewidth of the initial $v=0$ level exhibits a series of asymmetric peaks. The position of each of these peaks shifts considerably when ${\ensuremath{\omega}}_{1}$ is changed. The energy of the intermediate resonance in the closed channel corresponding to the absorption of a single ${\ensuremath{\omega}}_{1}$ photon strongly depends on the second frequency, ${\ensuremath{\omega}}_{2}.$ The peaks against ${\ensuremath{\omega}}_{2}$ occur whenever this resonance, with a dominant $v=6$ character, coincides in energy with the Stark shifted $v=0$ level in the initial closed channel.