Time-dependent vibrational sum-frequency generation spectroscopy of the air-water interface

Naveen Kumar Kaliannan,Thomas D Kühne,Deepak Ojha

doi:10.1038/s42004-019-0220-6

Naveen Kumar Kaliannan, Thomas D Kühne + Show 1 more

Open Access

https://doi.org/10.1038/s42004-019-0220-6

Copy DOI

Journal: Communications Chemistry	Publication Date: Oct 15, 2019
Citations: 21	License type: open-access

Affiliation: Paderborn University

Abstract

Vibrational sum-frequency generation spectroscopy is a powerful method to study the microscopic structure and dynamics of interfacial systems. Here we demonstrate a simple computational approach to calculate the time-dependent, frequency-resolved vibrational sum-frequency generation spectrum (TD-vSFG) of the air-water interface. Using this approach, we show that at the air-water interface, the transition of water molecules with bonded OH modes to free OH modes occurs at a time scale of sim3 ps, whereas water molecules with free OH modes rapidly make a transition to a hydrogen-bonded state within sim2 ps. Furthermore, we also elucidate the origin of the observed differential dynamics based on the time-dependent evolution of water molecules in the different local solvent environments.

Highlights

Vibrational sum-frequency generation spectroscopy is a powerful method to study the microscopic structure and dynamics of interfacial systems
Conventional 2D-vibrational sum-frequency generation (vSFG) spectroscopy permits to study the coherence generated by irradiation of electric fields as a function to time-delay between the applied fields
A major difference between the two techniques is that 2D-vSFG measures the fourth-order susceptiblity, i.e. χ4ðωÞ, whereas time-resolved vSFG or IR-pump vSFG-probe spectroscopy collects the χ2ðωÞ as a function of applied IR-pump pulse

Summary

Introduction

Vibrational sum-frequency generation spectroscopy is a powerful method to study the microscopic structure and dynamics of interfacial systems. We demonstrate a simple computational approach to calculate the time-dependent, frequency-resolved vibrational sum-frequency generation spectrum (TD-vSFG) of the air-water interface. Ron Shen and coworkers experimentally demonstrated for the first time the applicability of vSFG spectroscopy to study the air–water interface[11,12,13] This technique has been further extended to more complex experimental setups like phase-sensitive vSFG, timeresolved vSFG, two-dimensional vSFG (2D-vSFG) to name just a few[14,15,16,17,18,19,20,21,22,23,24,25,26,27,28]. Our results support the existence of structural inhomogeneities at the air–water interface[53]

Methods

Results

Conclusion