Vibrational relaxation from electronically photoexcited states in solutionstudied by the acoustic peak delay method: hydrogen bonding effect to betaine-30

The rate of the temperature rise, which represents the vibrational relaxati on rates of many vibrational levels in the excited and the ground states, i s studied in various solvents by using the peak delay method of the transie nt acoustic grating after the S3 --> S0 internal conversion of betaine-30. It is found that a small amount of water efficiently relaxes the vibrationa l energy. The rate shows a clear correlation with the number of the hydroxy group of the solvent per unit volume. We interpreted this correlation as e vidence that the energy of the solute transferred to solvent efficiently th rough the hydrogen bonding. (C) 1999 Elsevier Science B.V. All rights reser ved.