Orientational dynamics of hydrogen-bonded phenol.

We use femtosecond mid-infrared pump-probe spectroscopy to study the effects of hydrogen bonding on the orientational dynamics of the OD-stretch vibration of phenol-d. We study two samples: phenol-d in chloroform and phenol-d in chloroform to which we added excess acetone. For phenol-d in chloroform, we observe rotational diffusion of the OD group around the CO bond, with a correlation time of 3.7 ps. For phenol-d hydrogen bonded to acetone, the reorientation time is strongly dependent on the probe frequency, varying from 3 ps on the blue side of the spectrum to more than 30 ps on the red side. (c) 2004 American Institute of Physics.