Analysis of rotational diffusion of coumarin laser dyes

Rotational diffusion analysis of two laser dyes, coumarin 6 and coumarin 30, has been studied in alkane and alcohol solvents using steady-state and time-resolved fluorescence depolarization methods. The rotational diffusion times of these probes vary linearly as a function of viscosity over the range of temperature studied. It is observed that the rotational diffusion time measurements of molecules in alcohol and alkane have relaxation times typically on the order of picoseconds, though they are greater in alcohol than in alkane solvents. However, it was observed that coumarins rotate faster in n-hexane and n-heptane than in n-propanol and n-butanol solvents, and the observed results are discussed in the last section.