We report the energy relaxation of the OH stretch vibration of HDO molecules contained in an HDO:D2O water bridge using femtosecond mid-infrared pump-probe spectroscopy. We found that the vibrational lifetime is shorter (∼630 ± 50 fs) than for HDO molecules in bulk HDO:D2O (∼740 ± 40 fs). In contrast, the thermalization dynamics following the vibrational relaxation are much slower (∼1.5 ± 0.4 ps) than in bulk HDO:D2O (∼250 ± 90 fs). These differences in energy relaxation dynamics strongly indicate that the water bridge and bulk water differ on a molecular scale.

Phys. Chem. Chem. Phys.
Ultrafast Spectroscopy

Piatkowski, L, Wexler, A.D, Fuchs, E.C, Schoenmaker, H, & Bakker, H.J. (2012). Ultrafast vibrational energy relaxation of the water bridge. Phys. Chem. Chem. Phys., 14(18), 6160–6164. doi:10.1039/C1CP22358E