COLLISION-INDUCED INTERSYSTEM CROSSING IN NH(A1-DELTA)-]NH(X3-SIGMA-)

Laser-induced fluorescence (LIF) of individual rovibronic states of gas-phase NH(a1-DELTA) and NH(X3-SIGMA-) is used to study intersystem crossing (isc) induced by collisions with N2, CO, Xe, and O2. Hydrazoic acid, HN3, is photolyzed at 266 nm to produce NH(a1-DELTA). The time-dependent behavior of NH(a1-DELTA) in its ground and excited vibrational levels is probed by LIF. Appearance rates for NH(X3-SIGMA-) in several vibrational levels are also measured. The vibrational level distribution of NH(X3-SIGMA-) is measured and compared to prior distribution calculations in order to predict the position of the potential energy curve crossing for the collision-induced isc. The results of these measurements on the mechanism of NH(a1-DELTA) decay are discussed in light of recent theoretical calculations and by comparison to isc occurring in the isoelectronic O(1D).