VIBRATIONAL PREDISSOCIATION OF ARCL2 - TOWARD THE DETERMINATION OF THE POTENTIAL-ENERGY SURFACE OF THE B-STATE

Accurate quantum mechanical calculations are carried out to test the s ensitivity of the spectroscopy and dynamics of the B state of ArCl2 to the steepness of the Morse term, alpha, of an atom-atom potential. It is discovered that the predissociation dynamics for this molecule are very complicated even in the Delta v=-1 regime due to resonances in t he continuum manifold of states. In both the Delta v=-1 regime and the Delta v=-2 regime the rate of vibrational predissociation and the pro duct rotational distribution are extremely sensitive to the value chos en for alpha, but not in a regular way. For the Delta v=-2 regime the variations can be attributed to spacings between resonances and the ov erlaps of the bright state wave functions with nearby dark states as e xpected from the intramolecular vibrational relaxation model. In the D elta v=-1 regime, the variations are shown to originate from resonance s in the v-1 continuum set of states. Although this makes it difficult to determine the value for alpha, a value of 1.8 Angstrom(-1) is prob ably close to the true value. The most useful new data to determine th e potential would be measurements of the lifetimes for as many vibrati onal levels as possible and rotational distributions for excitation to low vibrational levels of the B state. (C) 1996 American Institute of Physics.