Reorientation-induced relaxation of free OH at the air/water interface revealed by ultrafast heterodyne-detected nonlinear spectroscopy

Water’s hydrogen-bond network is truncated at hydrophobic interfaces and the dynamics of the resulting free OH groups is not well understood. The authors experimentally show that the main vibrational relaxation mechanism for free OH at the air-water interface is a diffusive molecular reorientation, rather than intramolecular energy transfer