PRODUCT ENERGY CORRELATIONS IN THE DISSOCIATION OF OVERTONE EXCITED NO DIMER

The photodissociation spectra, predissociative lifetime, fragment internal state and translational energy distributions, and product energy and vector correlations of overtone excited nitric oxide dimer, (NO)2, have been measured using pulsed molecular beam and Doppler profile analysis techniques. The nu-1 + nu-5 and 2-nu-5 modes of (NO)2 were excited by infrared pumping, and NO fragments were detected with sub-Doppler resolution by laser-induced fluorescence. The predissociative lifetimes of nu-1 + nu-5 and 2-nu-5 excited NO dimer are 34 +/- 6 and 20 +/- 3 ps, respectively. At least 97% of the dissociations produce NO(upsilon = 1) + NO(upsilon = 0); no product in the (upsilon = 0) + (upsilon = 0) channel was detected. For both modes, about 85% of the energy available after vibrational energy distribution goes into relative translational energy of the fragments. Only 3% of this available energy appears in fragment rotational energy. The propensities of the three spin-orbit correlated channels were measured for both modes. For nu-1 + nu-5 excitation 77 +/- 7% of the fragments are formed along the 2-PI-1/2-2-PI-3/2 channel and 21 +/- 5% via 2-PI-1/2-2-PI-1/2. In contrast, 39 +/- 6% of the dissociations following 2-nu-5 excitation proceed via the 2-PI-1/2-2-PI-1/2 channel. The only nonzero vector correlation observed is the fragment recoil anisotropy, which depends on the rotational transition excited in the parent. The results are discussed in terms of the dissociation and energy partitioning mechanisms.