State-resolved translation energy distributions for NCO photodissociation

The photodissociation dynamics of NCO have been examined using fast beam ph otofragment translational spectroscopy. Excitation of the 1(0)(2), 3(0)(1), and 1(0)(2)3(0)(2) transitions of the (B) over tilde (2)Pi<--<(X)over tild e> (2)Pi band produces N(S-4) + CO photofragments exclusively, while excita tion of the 1(0)(3)3(0)(3) transition yields primarily N(D-2) + CO photopro ducts. The translational energy [P(E-T)] distributions yield D-0(N-CO) = 2. 34 +/-0.03 eV, and DeltaH(f,0)(0)(NCO) = 1.36 +/-0.03 eV. The P(E-T) distri butions exhibit vibrationally resolved structure reflecting the vibrational and rotational distributions of the CO product. The N(D-2) + CO distributi on can be fit by phase space theory (PST), while the higher degree of CO ro tational excitation for N(S-4) + CO products implies that NCO passes throug h a bent geometry upon dissociation. The P(E-T) distributions suggest that when the (B) over tilde (2)Pi<--<(X)over tilde> (2)Pi band is excited, NCO undergoes internal conversion to its ground electronic state prior to disso ciation. Excitation of NCO at 193 nm clearly leads to the production of N(D -2) + CO fragments. While conclusive evidence for the higher energy O(P-3) + CN(X (2)Sigma (+)) channel was not observed, the presence of this dissoci ation pathway could not be excluded. (C) 2001 American Institute of Physics .