Molecular dynamics of ß-carotene in solution by resonance enhanced optical Kerr effect

Year: 1995

Authors: Ricci M., Torre R., Foggi P., Kamalov V., Righini R.

Autors Affiliation: European Laboratory for Non-linear Spectroscopy, University of Florence, Largo E. Fermi 2, 50125 Florence, Italy; Department of Chemistry, University of Florence, 50121 Florence, Italy; Photochemistry Department, Institute of Chemical Physics, Academy of Science, Kosygin Street, Moscow 117977, Russian Federation; Department of Chemistry, University of Basilicata, Potenza, Italy

Abstract: The orientational dynamics of ß-carotene in n-alkane solutions is investigated by resonance enhanced optical Kerr effect. By use of this spectroscopic technique, it is possible to selectively investigate the relaxation of a probe molecule at a concentration level low enough to allow the observation of the averaged single-molecule dynamics. For delay times longer than ~20 ps all solutions show a single exponential decay, with a time constant depending on the viscosity, that is ascribed to the ß-carotene orientational relaxation. The dependence on viscosity of the measured relaxation times is compared with the predictions of different models. The purely hydrodynamic theories overestimate, by far, the solute effective volume and hence its orientational relaxation time; a much better agreement is obtained from two quasihydrodynamic models.

Journal/Review: THE JOURNAL OF CHEMICAL PHYSICS

Volume: 102 (24)      Pages from: 9537  to: 9543

KeyWords: Depolarized Rayleigh-scattering; Rotational diffusion
DOI: 10.1063/1.468769