title: Direct infrared absorption spectroscopy of benzene dimer.
abstract: The direct infrared (IR) absorption spectrum of benzene dimer formed in a free-jet expansion was recorded in the 3.3 μm region for the first time. This has led to the observation of the C-H stretching fundamental mode ν(13) (B(1u)), which is both IR and Raman forbidden in the monomer. Moreover, the IR forbidden and Raman allowed ν(7) (E(2g)) mode has been observed as well. These two modes were found to be red-shifted along with the IR allowed ν(20) (E(1u)) mode, as previously reported by Erlekam et al. [Erlekam; Frankowski; Meijer; Gert von Helden J. Chem. Phys.2006, 124, 171101], using ion-dip spectroscopy, contrary to the blue-shift predicted earlier by theoretical studies. The observation of the ν(13) band indicates that the symmetry is reduced in the dimer, confirming the T-shaped structure observed by Erlekam et al. Our experimental results have not provided any direct evidence for the presence of the parallel displaced geometry, the main objective of the present work, as predicted by theoretical calculations.
authors.affiliation: Astrochimie Expérimentale, Institut de Physique de Rennes, UMR 6627 CNRS-Université de Rennes 1, Rennes, France.
authors.forename: Vijayanand
authors.initials: V
authors.lastname: Chandrasekaran
authors.forename: Ludovic
authors.initials: L
authors.lastname: Biennier
authors.forename: E
authors.initials: E
authors.lastname: Arunan
authors.forename: Dahbia
authors.initials: D
authors.lastname: Talbi
authors.forename: Robert
authors.initials: R
authors.lastname: Georges
mesh_terms: D001554:Benzene / Q000737:chemistry*; D019281:Dimerization; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared
chemical_list: D001554:Benzene