Solvent relaxation of oxazine-4 in 2-methyltetrahydrofuran Original Research Article

Time resolved and stationary fluorescence spectra of oxazine-4 perchlorate in 2-methyltetrahydrofuran (2-MTHF) were measured from 80 to 250 K. In the time resolved experiments the relaxation of the polar solvent around the chromophore was observed. Assuming a simple Debye relaxation behavior, relaxation times were extracted and from an Arrhenius analysis an activation energy of EA = 1320 cm−1 was estimated. The temperature dependent steady state fluorescence spectrum could be simulated using the obtained Arrhenius parameters. It was observed that exciting vibrational degrees of freedom in the chromophore leads to an acceleration of the solvent relaxation. As a probable reason a locally heating, caused by vibrational relaxation prior to the reorganization of the solvent shell is discussed.