Overdamped wavepacket motion along a barrierless potential energy surface in excited state isomerization
✍ Scribed by Arkady Yartsev; Jose-Luis Alvarez; Ulf Åberg; Villy Sundström
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 746 KB
- Volume
- 243
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
The wavepacket motion, associated with the barrierless excited state isomerization of the cyanine molecule 1,1'-diethyl-4,4'-cyanine in alcohol solutions, has been investigated using the fluorescence up-conversion technique. A viscosity-dependent ultrafast spectral shift of the fluorescence band was observed in agreement with predictions of earlier transient absorption studies. The shift appears as a fast decay (= 1 ps for propanol and = 2.5 ps for hexanol) in the blue part of the fluorescence band and as a fast risetime for longer wavelengths. The observed spectral shift is a direct manifestation of the bound-twisting process of the isomerization and indicates that vibrational relaxation, solvent dynamics or Franck-Condon non-active modes do not play an important role.