Polarization-xensitive CARS of excited-state rhodamine 6G: induced ansisotropy effects on depolarization ratios
| Autor: | Lucassen, Gerald W., Lucassen, Gerald, de Boeij, Wim P., Greve, Jan |
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| Přispěvatelé: | Faculty of Science and Technology, Optical Sciences |
| Rok vydání: | 1993 |
| Předmět: |
010401 analytical chemistry
METIS-129428 Analytical chemistry 01 natural sciences Molecular physics 0104 chemical sciences 010309 optics Rhodamine 6G Rhodamine symbols.namesake Vibronic coupling chemistry.chemical_compound chemistry IR-98800 Excited state 0103 physical sciences symbols Depolarization ratio Raman spectroscopy Ground state Instrumentation Spectroscopy Raman scattering |
| Zdroj: | Applied spectroscopy, 47(12), 1975-1988. Society for Applied Spectroscopy |
| ISSN: | 0003-7028 |
| Popis: | Resonance polarization-sensitive coherent anti-Stokes Raman scattering (PS CARS) spectra of the electronic ground state and excited singlet S1 state of rhodamine 6G in ethanol were obtained with the use of the pump-probe technique with nanosecond time resolution. Variation of the polarization orientation of the pump laser beam showed differences in the excited-state spectra due to optically induced anisotropy. The pure electronic susceptibility of ground-state rhodamine 6G was shown to be small in comparison with nonresonant susceptibility of the solvent, and was neglected in further analyses. The pure electronic susceptibility of excited rhodamine 6G was examined by coherent ellipsometry. The complex third-order susceptibility was analyzed by means of a nonlinear least-squares fit program that provides detailed information on the Raman vibration parameters, including depolarization ratios and phases. In the isotropic case the measured depolarization ratios are close to 1/3, whereas in the anisotropic case, ground-state depolarization ratios are 0.5–0.65 and in the excited state 0.17–0.22. Estimated depolarization ratio changes in ground-state and excited-state rhodamine 6G are in agreement with theoretically predicted values in the case of induced anisotropy under the assumption of parallel dipole moments of the CARS process. The effects of possible changed molecular structure or symmetry and changed enhancement of different electronic transitions cannot be determined without making some assumptions about one of these effects. The obtained phase differences reflect different enhancements and vibronic coupling for ground-state and excited-state vibrations. The ground-state and excited-state hyperpolarizabilities, [Formula: see text], of rhodamine 6G were estimated to be 3.8·10−35 esu and 27.4·10−35 esu, respectively. |
| Databáze: | OpenAIRE |
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