Greco Alessandro, Ohto Tatsuhiko, Nagata Yuki, Bonn Mischa, Backus Ellen H G
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
J Chem Phys. 2024 Nov 7;161(17). doi: 10.1063/5.0231310.
Water interfaces play a crucial role in regulating interactions and energy flow. Vibrational sum-frequency generation (vSFG) spectroscopy provides structural and dynamic information on water molecules at interfaces. It has revealed, for instance, the presence of the hydrogen-bonded and free OH groups at the air-water interface. Here, using temperature-dependent, time-resolved vSFG, we focus on the vibrational energy relaxation dynamics of interfacial heavy water (D2O). We reveal that while the relaxation timescale for hydrogen-bonded OD stretch modes is temperature-independent, the lifetime of the free OD stretch mode decreases with increasing temperature. Our data, supported by simulations, suggest that both intramolecular energy transfer and rotational reorientation mechanisms jointly contribute to the energy relaxation process of the free OD, with temperature influencing these mechanisms differently.
