Theoretical calculation of photodissociation cross sections for the Ar-H2 van der Waals complex

Accurate benchmark calculations of the photodissociaton cross sections for the Ar-H2 van der Waals molecule are presented. Both the bound ground state of the van der Waals molecule and the predissociative (or continuum) upper state are treated by solving sets of coupled differential equations. Calculation of the photodissociation cross section involves computation of the matrix element of the dipole moment function between the wave functions corresponding to these two states. These matrix elements are efficiently evaluated using the ‘‘artificial channel method.’’ Absolute values of photodissociation cross sections are presented for a large number of predissociative spectroscopic transitions. Cross sections for both vibrational and rotational predissociation processes are studied. The line shapes of the spectral absorption lines are obtained naturally by mapping out the total photodissociation cross sections over the width of the spectral transition. In some cases corresponding to high rotational states of the H2 photofragment, non-Lorentzian line shapes are observed. The quantum state distribution of the product photofragments are also reported.