ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Raman excitation profiles for twelve vibrational modes of the solvatochromic dye betaine-30 have been measured in CH3OH and CD3OD solutions at wavelengths that span the S0→S1 charge transfer transition. Though the absorption spectra of the dye are the same in the protonated and deuterated forms of the solvent, Raman cross-sections for all modes were found to be generally lower in the CH3OH solution than inCD3OD. The time-dependent theory of Heller was applied to model the absorption and Raman profiles, and both mono- and bi-exponential solvent relaxation were considered in order to account for solvent induced electronic dephasing. The two models lead to different physical pictures for the relevant solvent dynamics, but in either case the amplitude of solvent dephasing is reduced in deuterated compared to protonated methanol. The effect is interpreted in terms of stronger solvent–solute and solvent–solvent hydrogen bonding in deuterated methanol solution. Comparing to previous results for betaine-30 Raman cross-sections in acetonitrile [Y. Zong and J. L. McHale, J. Chem. Phys. 106, 4963 (1997)], it is concluded that slower solvent dynamics and perturbations to the electronic structure of betaine-30 lead to larger Raman intensities in methanol. The data suggest that solvent dynamics depend strongly on the electronic state of betaine-30. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.474708
Permalink
