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The unimolecular dissociation of the methoxycarbonyl, CH3OCO, radical is investigated. Photolysis of methyl chloroformate at 193 nm produced nascent CH3OCO radicals with a distribution of internal energies, determined by the velocities of the momentum-matched Cl atoms, that spans the theoretically predicted barriers to the Ch3O + CO and CH3 + CO2 product channels.

The title reaction was investigated at three different collision energies in a pulsed, crossed-beam apparatus. The (2+1) REMPI spectra of the CHD[sub 2] products revealed, in addition to the anticipated 4[sub m][sup n] vibronic bands, a hitherto unobserved feature. The new feature was shown and assigned to the 3[sub 1][sup 1] band. A time-sliced ion velocity imaging technique was applied to map out the coincident DF attributes of the two product states 4[sub 2] and 3[sub 1], whose energy levels lie nearly degenerate. Remarkably similar results were found for the two states in every aspect at all three collision energies. A simple model of Fermi-coupled states was proposed to rationalize this, at first sight, surprising finding. Implications to collisional processes which involve mixed molecular basis states in general are outlined. Possible quantum interference phenomenon is suggested. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The reaction of atomic chlorine with methane was studied in crossed-beam experiments at a collisional energy of E(sub c) approximately equal to 4.7 Kcal/mol. Several outstanding issues about the reaction of uncertainty or discrepancy on the vibrational enhancement factor for bending and/or torsional excited CH4 are addressed by using a time-sliced product imaging technique.