INTRAMOLECULAR VIBRATIONS OF THE PHENOL DIMER REVEALED BY SPECTRAL HOLE BURNING (SHB) AND DISPERSED FLUORESCENCE SPECTROSCOPY
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Date
1995
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Ohio State University
Abstract
In the hydrogen bridge bonded phenol dimer one phenol moiety is the proton donor, while the other acts as proton acceptor. The donor absorbs at longer, the acceptor at shorter wavelength than the monomer. We performed hole burning spectroscopy to rule out the existence of different conformers, absorbing in the investigated region. Holes burned in the population of the dimer are analyzed via fluorescence from the donor origin. Even acceptor vibrations could be analyzed this way, because acceptor and donor moiety belong to one species in the electronic ground state and share a common set of ground state levels. This is favorable, because the excited donor phenol fluoresces much more efficiently than the acceptor part. 10 low frequency modes of the donor and 8 of the acceptor moiety could be observed. In order to assign the low frequency vibrational bands to distinct normal modes dispersed fluorescence spectra have been taken, by pumping all intermolecular vibrations. The Franck Condon pattern then allows to assign unambiguously which level in the electronic ground state belongs to which excited state level.
Description
Author Institution: Heinrich-Heine Universität Düsseldorf, 40225 Düsseldorf, Germany