Journal of Chemical Physics, Vol.114, No.20, 9020-9027, 2001
State-resolved translation energy distributions for NCO photodissociation
The photodissociation dynamics of NCO have been examined using fast beam photofragment 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 tilde> (2)Pi band produces N(S-4) + CO photofragments exclusively, while excitation of the 1(0)(3)3(0)(3) transition yields primarily N(D-2) + CO photoproducts. 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) distributions exhibit vibrationally resolved structure reflecting the vibrational and rotational distributions of the CO product. The N(D-2) + CO distribution can be fit by phase space theory (PST), while the higher degree of CO rotational excitation for N(S-4) + CO products implies that NCO passes through 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 dissociation. 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 dissociation pathway could not be excluded.