Ultrafast Relaxation Processes of Triarylpyrylium Cations

Autor:	Renata Karpicz, V. Gulbinas, Thomas Gustavsson, Michèle Veber, Dimitra Markovitsi
Rok vydání:	2000
Předmět:	Absorption spectroscopy Chemistry Oscillator strength Excited state Intermolecular force Vibrational energy relaxation Relaxation (physics) Physics::Chemical Physics Physical and Theoretical Chemistry Chromophore Internal conversion (chemistry) Photochemistry
Zdroj:	The Journal of Physical Chemistry A. 104:5181-5189
ISSN:	1520-5215 1089-5639
DOI:	10.1021/jp9940248
Popis:	The time evolution of the fluorescence and the photoinduced absorption spectra of four triarylpyrylium cations, differing in the number of dodecyl chains attached to the chromophore, was studied by means of femtosecond fluorescence upconversion and picosecond pump-probe absorption techniques. The dependence on solvent viscosity was also examined. The results are rationalized in terms of excited and ground-state relaxation dynamics and may be differentiated into intramolecular conformational changes and intermolecular solutesolvent contributions. The dynamic fluorescence shift is related to solvent relaxation, whereas the fluorescence intensity decay is attributed to molecular twisting acting in an intricate manner. First, the geometrical relaxation reduces rapidly the fluorescence oscillator strength, but it also greatly enhances the nonradiative S 0 r S1 internal conversion rate. Molecular back-twisting combined with vibrational relaxation in the ground state is shown to be the last and the slowest process of the reaction.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::5f1ca491815daa40283c44238d1cc615 https://doi.org/10.1021/jp9940248 Zobrazit plný text záznamu