title: Tunneling splittings in the S0 and S1 states of the benzoic acid dimer determined by high-resolution UV spectroscopy.
abstract: Five different isotopologues of the benzoic acid dimer and a vibronic band located 57 cm(-1) above the electronic origin, which is assigned to the out-of-plane butterfly motion, are studied by rotationally resolved UV spectroscopy. From these measurements a ground-state structure with C(2h) symmetry is deduced, whereas the symmetry is lowered to C(s) in the S(1) state. The increase in the center-of-mass distance between the two monomers that is found on electronic excitation indicates a decrease in hydrogen-bond strength. The tunneling splittings in the S(0) and S(1) states are 1385.2+/-0.7 and 271.2+/-0.7 MHz, respectively, corresponding to an increase in barrier height by 7.2% on electronic excitation.
authors.affiliation: Molecular and Biophysics Group, Institute for Molecules and Materials, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands.
authors.forename: Ivo
authors.initials: I
authors.lastname: Kalkman
authors.forename: Chau
authors.initials: C
authors.lastname: Vu
authors.forename: Michael
authors.initials: M
authors.lastname: Schmitt
authors.forename: W Leo
authors.initials: WL
authors.lastname: Meerts
mesh_terms: D019817:Benzoic Acid / Q000737:chemistry*; D019281:Dimerization; D004583:Electrons; D015394:Molecular Structure; D013057:Spectrum Analysis; D014732:Vibration
chemical_list: D019817:Benzoic Acid