Journal of Physical Chemistry A, Vol.105, No.26, 6342-6352, 2001
The 193-nm photodissociation of NCO
The 193-nm photolysis of the NCO radical has been investigated. NCO was generated from the reaction of CN + O-2, 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 M-CO and the NC-O bonds may break. N(D-2,P-2) and CO products have been detected using vacuum ultraviolet laser induced fluorescence. A direct measurement of the N(D-2):N(P-2) 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 coproducts N(S-4,D-2,P-2). Combination of the results from the prior model and the direct measurement yielded a branching ratio of N(S-4):N(D-2):N(P-2) of (5.1 +/- 1.8):(93.6 +/- 4.8):(1.3 +/- 0.3). For the N(D-2) + CO product channel, the average energy disposal into product relative translation (8%) and CO vibration (24%) was determined, leaving 68% of the available energy to appear as CO rotation. This observation suggests that the geometry of the dissociating state of NCO is likely bent.