Tunneling Splittings in the S0 and S1 States of the Benzoic Acid Dimer Determined by High‐Resolution UV Spectroscopy |
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| Authors: | Ivo Kalkman Chau Vu Michael Schmitt Dr W Leo Meerts Prof |
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| Institution: | 1. Molecular and Biophysics Group, Institute for Molecules and Materials, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen (The Netherlands), Fax: (+31)?24‐365‐33‐11;2. Institut für Physikalische Chemie und Elektrochemie I, Mathematisch‐Naturwissenschaftliche Fakult?t, Heinrich‐Heine‐Universit?t Düsseldorf, Universit?tsstra?e 26.43.02.43, 40225 Düsseldorf (Germany), Fax: (+49)?211‐81‐15195 |
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| 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 C2h symmetry is deduced, whereas the symmetry is lowered to Cs in the S1 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 S0 and S1 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. |
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| Keywords: | benzoic acid dimerization hydrogen bonds laser spectroscopy structure elucidation |
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