Energy transfer in liquid phase

Energy transfer dynamics in liquid phase have been investigated in different frequency regimes. Firstly, vibrational energy relaxation is studied with a small ion molecule (N{dollar}sb3sp-{dollar}) in protic solvents (H{dollar}sb2{dollar}O, D{dollar}sb2{dollar}O, CH{dollar}sb3{dollar}OH, C{dollar}sb2{dollar}H{dollar}sb5{dollar}OH). Vibrational relaxation times ({dollar}Tsb1 approx{dollar} 3ps) of azide ion were measured in different solvent environments utilizing a picosecond infrared pump-probe experiment with a time resolution of 1 ps. Possible vibrational relaxation mechanisms of azide ions in protic solvent environments are discussed, based on experimental results which reveal no concentration and solvent dependence on the measured {dollar}Tsb1{dollar} times of azide ions in D{dollar}sb2{dollar}O (0.03M, 0.1M, 0.3M) and other protic solvents. Secondly, the rate of intramolecular electronic excitation energy transfer in 9,9{dollar}spprime{dollar} bifluorene is investigated in a variety of solvents, using both time-correlated single photon counting and femtosecond fluorescence upconversion techniques. The kinetics of energy transfer were determined in both cases by time dependent fluorescence anisotropy measurements. The energy transfer dynamics between fluorene moieties has been found to occur on a time scale of approximately 600fs in different solvents and has been correlated with a {dollar}Tsb2{dollar} value of 70 fs (dephasing time of coherence between the two excited states) and {dollar}beta{dollar} (coupling energy between the states) obtained from jet measurements. The dihedral angle between the fluorene moieties was also calculated from the anisotropy measurements and compared with the values obtained from solution phase NMR studies. Thirdly, time-resolved fluorescence lifetime and fluorescence anisotropy measurements have been performed to investigate chemical dynamics of polysilane derivatives in solution. The physical processes responsible for the decay of the anisotropy are discussed. Finally, excited state intramolecular proton transfer reaction in 2-(2{dollar}spprime{dollar}-hydroxy-5{dollar}spprime{dollar}-t-octyl phenyl)benzo-triazole has been investigated using the time-correlated single photon counting technique. A systematic study of the proton transfer in 1-alkanols reveals that the proton transfer rate is close to the solvent longitudinal relaxation time, {dollar}tausb{lcub}rm L{rcub}{dollar}. Significant solvation of excited molecules did not occur during the proton transfer lifetime. It is thus concluded that the proton transfer is a tunneling process which is slowed down by the multidimensionality of the potential surface and by the solvent fluctuations.