Hydrogen atom release from methyl groups of energized molecules

Three diverse molecules, 2,3,4,5,6-pentafluorotoluene (PFT), trimethylamine (TMA), and methyl bromide were irradiated by weak 193.3 nm light. In each case hydrogen atoms were released, as the major channel for PFT and as a mi nor channel for the two others. The low average translational energy releas e, the isotropic angular distribution, and the linear excimer power depende nce all lead to the conclusion that the dissociation is from a very hot gro und state. The unimolecular dissociation is less selective than in the more usual unimolecular processes at much lower energies. During these experime nts an unusual multiphoton dissociation was found. Focusing 205.1 nm light on TMA produces H atoms with an average kinetic energy of 4.2 +/- 0.5 eV. ( C) 1999 American Institute of Physics. [S0021-9606(99)00720-5].