Energy Transfer in Single Hydrogen‐Bonded Water Molecules

Abstract We study the structure and dynamics of hydrogen‐bonded complexes of H 2 O/HDO and acetone dissolved in carbon tetrachloride by probing the response of the OH stretching vibrations with linear mid‐infrared spectroscopy and femtosecond mid‐infrared pump–probe spectroscopy. We find that the hydrogen bonds in these complexes break and reform with a characteristic time scale of ≈1 ps. These hydrogen‐bond dynamics are observed to play an important role in the equilibration of vibrational energy over the two OH groups of the H 2 O molecule. For both H 2 O and HDO, the OH stretching vibrational excitation relaxes with a time constant of 6.3±0.3 ps, and the molecular reorientation has a time constant of 6±1 ps.