title: Torsional vibrational structure of the propene radical cation studied by high-resolution photoelectron spectroscopy.
abstract: The pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the X̃(+2)A(")←X̃(1)A' transition of CH(3)CHCH(2) (propene), CD(3)CDCD(2), and several partially deuterated isotopomers have been recorded in the region of their adiabatic ionization thresholds and up to 2000 cm(-1) of internal energy of the cations. The vibrational structure has been assigned on the basis of the frequency shifts resulting from deuteration of selected sites of the propene molecule. Two highly anharmonic progressions have been identified and assigned to the two torsional modes of the propene cation, the methyl and methylene torsions. The positions of the torsional levels could be approximately reproduced using one-dimensional models, allowing a semi-quantitative description of the potential energy surface along each torsional coordinate. The observation of forbidden vibrational bands and the analysis of their partially resolved rotational contours reveal the importance of the vibronic coupling between the X̃(+2)A(") and the Ã(+2)A(') states mediated by the methylene (ν(20)) and methyl (ν(21)) torsional modes.
authors.affiliation: Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zurich, Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Vasilatou
authors.forename: F
authors.initials: F
authors.lastname: Merkt
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D015394:Molecular Structure; D056951:Photoelectron Spectroscopy; D011789:Quantum Theory; D014732:Vibration
chemical_list: D000475:Alkenes; D002412:Cations; D005609:Free Radicals; C013658:propylene