Vibrational predissociation and infrared spectrum of the Ar–HCl van der Waals molecule

The energies and lifetimes of bound and vibrationally predissociating states of Ar–HCl are calculated, using accurate close coupling calculations on the best available potential energy surface, and the selection rules governing the infrared spectrum are described. The vibrational predissociation lifetimes are of the order of microseconds; thus the resulting spectroscopic lines will be sharp (width <1 MHz), but the excited states will not survive to travel far down a molecular beam. The dominant predissociation product is found to be HCl in the highest accessible rotational level ( j=15). Perturbation theory calculations of the lifetimes and product state distributions are drastically in error.