Vibrational relaxation and dephasing of small molecules strongly interacting with water

Abstract

Nonlinear infrared experiments were used to measure vibrational relaxation and spectral diffusion processes of small molecules (CN-, N3-, CO2) in water. Vibrational relaxation of CN- is dominated by Coulomb interaction and intramolecular solvent modes are important to understand the mechanism. For N3- and CO2 the relaxation appears to be directly into the solvent without involvement of lower lying intramolecular modes. For both N3- and CO2, a structural inhomogeneity was observed, which decays on a ca. 1 ps time scale and which is attributed to the dynamics of the hydrogen bonds between water and the solute.