The 193-nm photolysis of the NCO radical has been investigated. NCO was generated from the reaction of CN + O2, where the CN was produced by 193-nm photolysis of C2N2 close to the nozzle of a pulsed jet. A second 193-nm photon dissociated the NCO radical during the same laser pulse. At this photon energy both the N-CO and the NC-O bonds may break. N(2D, 2P) and CO products have been detected using vacuum ultraviolet laser induced fluorescence. A direct measurement of the N(2D):N(2P) branching ratio yielded an upper limit of 72 +/- 18. The CO vibrational distribution was modeled with prior distributions for each of the contributing channels with co-products N(4S, 2D and 2P). Combination of the results from the prior model and the direct measurement yielded a branching ratio of N(4S): N(2D): N(2P) of (5.1 +/- 1.8):(93.6 +/- 4.8):(1.3 +/- 0.3). For the N(2D) + CO product channel, the average energy disposal into product relative translation (7%) and CO vibration (24%) was determined, leaving 69% of the available energy to appear as CO rotation. This observation suggests that the geometry of the dissociating state of NCO is likely to be bent.

The photodissociation spectroscopy and dynamics of free radicals is studied by the technique of fast beam photofragment translational spectroscopy. Photodetachment of internally cold, mass-selected negative ions produces a clean source of radicals, which are subsequently dissociated and detected. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states of the radical. In addition, the photodissociation dynamics, product branching ratios, and bond energies are probed at fixed photon energies by measuring the translational energy, P(E{sub T}), and angular distribution of the recoiling fragments using a time- and position-sensitive detector. Ab initio calculations are combined with dynamical and statistical models to interpret the observed data. The photodissociation of three prototypical hydrocarbon combustion intermediates forms the core of this work.