PHOTOFRAGMENT YIELD SPECTRA OF METHYL NITRITE IN A SUPERSONIC JET

Photofragment yield spectra of jet-cooled CH3ONO are measured over the first few resonances of the S1 <-- S0 absorption by monitoring the NO fragments via selected rotational levels in each of the four sublevels F1(A', A'') and F2 (A', A'') of the vibrational states upsilon'' = 0, 1 and 2. Based on spectral features, the 0(0)0 transitions of the anti- and syn-isomers were assigned to the bands at 2 5600 +/- 30 and 26160 +/- 30 cm-1, respectively, supporting, in combination with vibrational state distributions, the dominance of a vibrationally non-adiabatic over an adiabatic dissociation process. The observed linewidth of the vibronic absorption bands of almost-equal-to 500 cm-1, which is essentially unchanged from that at room temperature, remains unexplained.