122nd General Meeting of the KCS

Type Oral Presentation
Area Oral Presentation for Young Scholars in Physical Chemistry
Room No. Room 324A
Time THU 10:12-:
Code PHYS.O-7
Subject Origin of Zundel broadening explained via particular vibrational modes of Eigen structure altered by solvent environmental effects
Authors Yevhen Horbatenko*, Cheol Ho Choi*
Department of Chemistry, Kyungpook National University, Korea
Abstract Detailed molecular mechanism of the proton transfer in liquid water has been an intriguing issue, since it plays a crucial role in chemical as well as biological processes. To investigate the dynamics of the proton transfer, ultrafast infrared spectroscopy has been widely used. However, a broad continuous absorption band that appears in a region of ~1800–3000 cm–1 makes interpretation of spectra challenging task. Many theories have been proposed to interpret the origin of this broadening, but none of them seems satisfactory explains it. Here, ab initio molecular dynamics and instantaneous vibrational mode analysis of various protonated ice as well as water structures have been performed to understand the origin of the broadening in the infrared spectra. Based on the simulations, the origin of the broadening for the first time is explained via contribution from three OH stretching modes of the Eigen structure, i.e., symmetric A1 and asymmetric doubly degenerate E. The infrared spectrum of the gas-phase Eigen structure (hydronium with the first solvation shell) reveals that these three OH modes fall into one band. As shown, splitting of this band into three, e.g., in ice is caused by the second solvation shell. These bands are further broadened in liquid water due to random motions of the solvent molecules.
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