FRAGMENT ENERGY AND VECTOR CORRELATIONS IN THE OVERTONE-PUMPED DISSOCIATION OF HN3 X1A'

NH stretching overtone and combination states in HN3 X approximately 1A' were excited by IR-visible double resonance pumping and by direct overtone pumping in the range 6v1 (17 670 cm-1) to 7v1 (20 070 cm-1). NH fragments in the a 1-delta and X3-SIGMA- states were detected by laser induced fluorescence with sub-Doppler resolution to determine branching ratios, correlated fragment rotational state and kinetic energy distributions, and fragment vector correlations. The spin-forbidden triplet channel was accessible to all states excited, while the threshold for the singlet channel was determined to lie in the range 18 190 to 18 755 cm-1. The measured energy release places limits on the HN-NN bond energy, and the heights of barriers to reaction. The barrier in the singlet exit channel is at least 540 cm-1. The singlet channel accessed by 7v1 dissociation is characterized by a Boltzmann-like NH rotational distribution ([J(NH)] almost-equal-to 3.5) highly excited N2 rotations ([J(N2)] greater-than-or-equal-to 20), and total translational energy release peaked away from zero ([E(T)] almost-equal-to 1350 cm-1). Vector correlations and LAMBDA-doublet propensities indicate that nonplanar dissociation processes influence the NH rotations, but become less important for higher NH rotational states. The principal correlations are a strong positive recoil anisotropy (BETA almost-equal-to 0.6), a weak positive v-J correlation (BETA-vJ almost-equal-to 0.17), and a J(NH)-dependent LAMBDA-doublet propensity. A model using parent vibrational motion projected onto fragment rotation is suggested to explain these observations. The triplet channel exhibits similar NH and N2 rotational state distributions, with most of the available energy (substantially greater than in the singlet channel) appearing as fragment kinetic energy.