Abstract

In recent years a new frequency window has been opened: The THz range. We could show that THz absorption spectroscopy serves as a new tool to study solvation of biomolecules [1]. We have carried out an ab initio MD simulation to unravel the underlying molecular motions: In contrast to the mid infrared regime, where the absorption peaks can be assigned to intramolecular motions in the frequency regime below 1000 cm-1 intermolecular motions with concerted particle motions dictate the spectrum [2]. Precise measurements of absorption coefficients of solvated solutes yielded an increased absorption coefficient for water in the hydration shell. MD simulations were able to provide a more detailed molecular picture. These simulations showed that a retardation of the water dynamics in the vicinity of biomolecules is associated with an increase in absorption at 90 cm-1 and a decrease below 50 cm-1, in agreement with our experimental observation [3]. Using THz time domain systems it is possible to follow the changes in solvation dynamics on a psec time scale.

© 2011 Optical Society of America