Vibrational relaxation in the ground electronic state of large organic molecules in solution

A new and sensitive method for the study of vibrational relaxation in the ground electronic state of molecules has been applied to dilute solutions of Rhodamine 6G in alcohols. The method takes advantage of the large electronic cross sections to prepare the molecules in vibrationally excited states and probe their return to the ground state. The influence of the solvent on our experimental observations is discussed. A study of the effect of dielectric relaxation and hydrogen bonding on the Stokes shift justifies the interpretation of our results in terms of vibrational relaxation.