Internal conversion in the rhodamine Dye, fast acid violet 2R

Abstract

The results of fluorescence lifetime measurements of Fast Acid Violet 2R in a series of alcohols and diols having a wide range of viscosity have been fitted to Kramers' equation, an approximate solution of the Fokker–Planck differential equation, applicable in the case of conformational change, hindered by viscous drag of a solvent. Three unknown parameters in Kramers' equation were determined by a least-squares method. One of these parameters, d, the effective radius of the part of the molecule undergoing conformational change, was found to be > 4Å in normal alcohols indicating that solvent attachment takes place. The value of d in diols was anomalously low.