title: One-photon mass-analyzed threshold ionization spectroscopy of 2-chloropropene (2-C3H5Cl) and its vibrational assignment based on the density-functional theory calculations.
abstract: A high-quality mass-analyzed threshold ionization (MATI) spectrum of 2-chloropropene, 2-C3H5Cl, is reported. Its ionization energy determined for the first time from the 0-0 band position was 9.5395+/-0.0006 eV. Almost all the peaks in the MATI spectrum could be vibrationally assigned utilizing the frequencies calculated at the B3LYP6-311++G(3df,3pd) level and the Franck-Condon factors calculated with the molecular parameters obtained at the same level. In particular, the observed methyl torsional progression could be reproduced very well through quantum-mechanical calculations using the molecular parameters obtained at this level. Dramatic lowering of the torsional barrier inferred from the experimental data was entirely compatible with the B3LYP6-311++G(3df,3pd) results. The torsional barrier and the internal rotational constant determined by fits to six torsional peaks were 53.6 and 5.20 cm(-1), respectively. A brief discussion at the level of molecular orbital is presented to account for the dramatic lowering of the torsional barrier upon ionization.
authors.affiliation: National Creative Research Initiative Center for Control of Reaction Dynamics and School of Chemistry, Seoul National University, Seoul 151-742, Korea.
authors.forename: Yong Jin
authors.initials: YJ
authors.lastname: Bae
authors.forename: Mina
authors.initials: M
authors.lastname: Lee
authors.forename: Myung Soo
authors.initials: MS
authors.lastname: Kim