ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Direct observation of all three photofragmentation channels of HNCO gives the relative yields of 3NH+CO, H+NCO, and 1NH+CO at nine different photolysis energies for both thermal and vibrationally excited molecules. Each higher energy channel dominates as it becomes accessible, but vibrational excitation changes the relative yield of 1NH markedly. Photolysis of HNCO(3ν1) at the same total energy yields up to 2.5 times more NCO with a corresponding reduction in 1NH. The relative yield of 3NH and NCO, however, is indifferent to vibrational excitation. The dependence of the yields on vibrational excitation supports a picture in which direct decomposition on the S1 surface produces 1NH+CO and in which internal conversion to S0 leads to H+NCO, by spin-allowed unimolecular decay, and to 3NH+CO, by intersystem crossing and decomposition on T1. The observed vibrational enhancement of the NCO yield is consistent with vibrational excitation impeding the decomposition to 1NH+CO on S1 and, thus, increasing the number of molecules that cross to S0 and decay to H+NCO. © 2001 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1371283
