Excimer Laser Fragmentation Studies of Selected Oximes: Nascent OH InternalEnergy Distributions and the Search of H2CN Fluorescence

摘要

Excimer laser excitation (193 nm) of formaldoxime (H2 CN-OH) or the methylatedhomologs, R2R2CH-OH where R1, R2 = H or CH3, results in dissociation. The upper limit for the quantum yield of fluorescence of the R1R2CN is estimated to be between 1-10% depending on the precursor used. The OH companion radical was probed by laser induced fluorescence (LIF) utilizing the A-X (2-1) and (1,0) bands near 34700 cm-1, and the nascent rotational, vibrational, and ground electronic state spin-orbit distributions determined. No laser induced fluorescence of the R1R2CN radical could be observed upon irradiation in the regions where the radicals are known to absorb, 280 to 295 nm. From the nascent OH product distributions, we calculate that only 2.5 Kcal/mole of the excess energy appears as OH product internal energy, thus leaving about 80 Kcal/mole to be divided between the R1R2CN fragment and translation. We, therefore, conclude that it is highly likely that the upper states of these radicals probed in the 280 to 295 nm region are predissociative. (jes)