15min:

W. M. FAWZY, G. KERENSKAYA AND M. C. HEAVEN, Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, GA 30322.

The H₂-NH(X) van der Waals complex has been examined using ab initio theory and detected via fluorescence excitation spectroscopy of the A³ - X^{3 -} transition. Electronic structure calculations show that the minimum energy geometry corresponds to collinear H₂-NH(X), with a well depth of D_e=116 cm^-1. The potential energy surface supports a secondary minimum for a T-shaped geometry, where the H atom of NH points towards the middle of the H₂ bond (C₂v point group). For this geometry the well depth is 73 cm^-1. Laser excitation spectra for the complex show transitions to the H₂+NH(A) dissociative continuum. The onset of the continuum establishes a binding energy of D₀=32\pm2 cm^-1 for H₂-NH(X). Fluorescence from bound levels of H₂-NH(A) was not detected, most probably due to rapid reactive decay (H₂-NH(A) H+NH₂). The complex appears to be a promising candidate for studies of the photo-initiated H₂+NH abstraction reaction under conditions were the reactants are pre-aligned by the van der Waals forces.