TRANSLATIONAL ENERGY STUDY OF CH3 PHOTOFRAGMENTS FOLLOWING 1(N,PI-STAR) EXCITATION OF ACETONE

Excitation of a molecular beam of acetone at 266 nm leads to methyl photofragments that have been examined by resonant multiphoton ionization/time-of-flight mass spectrometry. Analysis of the arrival time profile of CH3+ reveals a broad translational energy distribution for vibrationless methyl photofragments, with mean energy EBAR(T) = 45.8 +/- 4.0 kJ mol-1. The CH3 0(0) photofragments are ejected isotropically in space. The mean photofragment recoil energy for two-body dissociation agrees with a recent determination of the acetone dissociation barrier height. Results are discussed in the context of related experiments on alpha-cleavage dynamics of acetic acid.