Reduced coupling of water molecules near the surface of reverse micelles

We report on vibrational dynamics of water near the surface of AOT reverse micelles studied by narrow-band excitation, mid-IR pump–probe spectroscopy. Evidence of OH-stretch frequency splitting into the symmetric and asymmetric modes is clearly observed for the interfacial H2O molecules. The polarization memory of interfacial waters is preserved over an exceptionally extended >10 ps timescale which is a factor of 100 longer than in bulk water. These observations point towards negligibly small intermolecular vibrational coupling between the water molecules as well as strongly reduced water rotational mobility within the interfacial water layer.

On the relation between the echo-peak shift and Brownian-oscillator correlation function

We show that for systems that exhibit bimodal dynamics in their system-bath correlation function the shift of the stimulated photon-echo maximum as a function of waiting time reflects fairly well the long time part of the correlation function. For early times this correspondence breaks down due to a fundamentally different behaviour of the echo-peak shift in this time domain and because of the effect of finite pulse duration on the echo-peak shift. The method is used to characterize the solvation dynamics in various dye solutions.

Hydrated-electron population dynamics

A detailed frequency-resolved pump-probe study of hydrated electron dynamics, performed with 5-fs pulses, is presented. We show that the experimental data can be successfully described with a model in which the excited state lifetime is similar to50 fs in regular water and similar to70 A in heavy water. The deuteration effect on the lifetime strongly suggests that OH-vibrational modes in the first solvation shell act as accepting modes for energy relaxation. (C) 2004 Elsevier B.V. All rights reserved