title: Distributions of angular anisotropy and kinetic energy of products from the photodissociation of methanol at 157 nm.
abstract: We investigated distributions of angular-anisotropy parameter beta and kinetic energy of fragments after photodissociation of methanol using time-of-flight (TOF) mass spectrometry. Fragments, in particular CH(3)O and CO, were successfully detected using tunable radiation from a synchrotron for photoionization. Following O-H bond fission, a CH(3)O fragment with internal energy greater than 104 kJ mol(-1) dissociates to CH(2)O+H. Elimination of two H(2) accompanies formation of CO. The beta value of hydroxyl hydrogen is -0.26 whereas that of methyl hydrogen is zero. H(2) has two distinct components in TOF spectra; these rapid and slow components have beta values -0.30 and -0.18, respectively. The CH(3)+OH dissociation exhibits a highly anisotropic angular distribution with beta= -0.75. The beta values of fragments from CD(3)OH photolysis are addressed. From measurements of angular-anisotropy parameters of various fragments, we surmise that the transition dipole moment mu is almost perpendicular to the C-O-H plane and that n-3p(x) (2 (1)A") is the major photoexcited state at 157 nm.
authors.affiliation: National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30077, Taiwan. shlee@nsrrc.org.tw
authors.forename: Shih-Huang
authors.initials: SH
authors.lastname: Lee
authors.forename: Hsin-I
authors.initials: HI
authors.lastname: Lee
authors.forename: Yuan T
authors.initials: YT
authors.lastname: Lee