Dynamics of the vibrational predissociation of HCl dimer

A comprehensive study of the vibrational predissociation dynamics of the HC l dimer is reported. The predissociation lifetimes for three H-Cl stretch v ibrationally excited states of ((HCl)-Cl-35)(2) have been measured. Compani on measurements for the (HCl)-Cl-35 . (HCl)-Cl-37 complex have also been ma de. These lifetimes range from 16(2) to 46(5) ns, lifetimes that are more t han 10(6) times longer than the H-Cl stretch vibrational period. The correl ated HCl(v' = 0,j(')) + HCl(v' = 0,j(')) fragment rotational state distribu tions have also been determined. These show a predominant dynamical bias th at favors the production of j',j " pairs that maximize the rotational energ y of the fragments and minimize their translational energy. The j',j " dist ribution is well described by a simple energy gap model of the dissociation . The results suggest a complex, for which there are substantial excursions from the equilibrium geometry, dissociation from a wide range of geometrie s, weak coupling of the H-Cl stretch vibrations to the dissociation coordin ate, and a blurring of the distinction between hydrogen bonded and free HCl moieties. These results are consistent with theoretical studies of the HCl dimer potential energy surface. (C) 2000 American Institute of Physics. [S 0021-9606(00)01532-4].