| Autor: |
Pavel Matousek, Anthony W. Parker, W.T. Toner, John N. Moore, Michael Towrie, Ronald E. Hester |
| Rok vydání: |
1993 |
| Předmět: |
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| Zdroj: |
Chemical Physics Letters. 208:471-478 |
| ISSN: |
0009-2614 |
| DOI: |
10.1016/0009-2614(93)87175-3 |
| Popis: |
Picosecond time-resolved resonance Raman spectra of singlet excited trans-stilbene have been obtained using several photolysis (pump) and Raman excitation (probe) wavelengths. Vibrational mode-selective changes in peak wavenumbers and bandwidths are dependent on the sample temperature, the pump wavelength, and the solvent. The effects are greatest for the band at ≈ 1570 cm −1 , attributed to the olefinic bond stretching mode. The peak wavenumber of this band decreases and the band broadens as the temperature is raised. Excess energy of excitation results in an initial decrease of peak wavenumber and increase in width followed by an increase in peak wavenumber and decrease in width as the delay between pump and probe increases further, with a similar time dependence for peak position as for width. Fits to the sum of two exponentials give time constants in the range 1 to 5 ps for the initial and 9 to 12 ps for the later stages of the evolution. There is an similarity between the temperature and excess energy dependence, but bandwidth is more (× 2.9) sensitive than peak wavenumber to excess energy. The mode-selective changes and dynamics are interpreted with a model involving intramolecular vibrational relaxation and reorientation of the solvent cage in response to microdielectric stabilisation forces and quasi-equilibration with bulk solvent. The role of vibrationally “'hot” low-wavenumber modes is clarified. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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