title: Observation of photochemical C-N bond cleavage in CH3N3: a new photochemical route to cyclic N3.
abstract: We report VUV-photoionization based photofragmentation-translational spectroscopy data, providing a comprehensive study of the collision free photochemistry of methyl azide (CH3N3) at 193 nm. We report the first observation of the production of methyl and the N3 radical and derive the translational energy release distribution of this reaction. The most probable translation energy is only 8%, and the maximum translational energy is only 60% of the available energy, taking CH3 + linear N3 as the zero of energy. However, the maximum translational energy release is quantitatively consistent with production of the higher energy isomer cyclic N3. Threshold photoionization of the N3 fragment using tunable synchrotron radiation shows results consistent with theoretical predictions of the cyclic N3 ionization potential. The secondary dissociation of N3 --> N(2D) + N2 is also observed and its translational energy release is derived. This distribution peaks at approximately 6 and extends to 11 kcal/mol as would be expected from the size of the exit channel barrier for spin-allowed dissociation of cyclic N3 (7 kcal/mol) and, furthermore, inconsistent with the barrier height of the spin-allowed dissociation of linear N3 (3 kcal/mol). A large fraction (approximately 45%) of the N3 does not dissociate on the microsecond time scale of the experiment suggesting methyl azide may be the most attractive photochemical precursor of cyclic N3 yet found.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara 93106-9510, USA. clarson@chem.ucsb.edu
authors.forename: Christopher
authors.initials: C
authors.lastname: Larson
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Ji
authors.forename: Peter C
authors.initials: PC
authors.lastname: Samartzis
authors.forename: Alfredo
authors.initials: A
authors.lastname: Quinto-Hernandez
authors.forename: Jim Jr-Min
authors.initials: JJ
authors.lastname: Lin
authors.forename: Tao-Tsung
authors.initials: TT
authors.lastname: Ching
authors.forename: Chanchal
authors.initials: C
authors.lastname: Chaudhuri
authors.forename: Shih-Huang
authors.initials: SH
authors.lastname: Lee
authors.forename: Alec M
authors.initials: AM
authors.lastname: Wodtke