Two-Dimensional Infrared Spectroscopy of Isotope-Diluted Low Density Amorphous Ice

Abstract

We present two-dimensional (2D) infrared (IR) spectra of isotope diluted ice in its low density amorphous form. Amorphous ice, which is structurally more similar to liquid water than to crystalline ice, provides higher resolution spectra of the hydrogen bond potentials because all motion is frozen. In the case of OD vibration of HOD in H2O, diagonal and off-diagonal (intermode) anharmonicity as well as the relaxation rate of the first excited state increase with hydrogen bond strength in a consistent way. For the OH vibration of HOD in D2O, additional more specific couplings need to be taken into account to explain the 2D IR response, that is, a Fermi resonance with the HOD bend vibration and couplings to phonon modes that lead to quantum beating. The lifetime of the fist excited state, 240 fs, is the shortest ever reported for any phase of isotope diluted water. We present 2D IR spectra of isotope diluted ice in its low density amorphous form. Amorphous ice, which is structurally more similar to liquid water than to crystalline ice, provides higher resolution spectra of the hydrogen bond potentials because all motion is frozen. In the case of OD vibration of HOD in H2O, diagonal and off-diagonal (inter-mode) anharmonicity as well as the relaxation rate of the first excited state increases with hydrogen bond strength in a consistent way. For the OH vibration of HOD in D2O, additional more specific couplings need to be taken into account to explain the 2D IR response, that is, a Fermi resonance with the HOD bend vibration and couplings to phonon modes that lead to quantum beating. The lifetime of the fist excited state, 240 fs, is the shortest ever reported for any phase of isotope diluted water.

Two-dimensional infrared spectroscopy of neat ice Ih

“…This provides a combination of structural and temporal sensitivity. The method has been applied to neat liquid water, [31][32][33][34][35][36][37] liquid water under confined conditions, [38][39][40] water in dilute solutions, [41][42][43] amorphous ice, [44][45][46] and the supercooled state. 47 Diagonal peaks arising from exciting one vibration and probing it again at a later time reveal information about spectral diffusion.…”

Communication: Disorder-suppressed vibrational relaxation in vapor-deposited high-density amorphous ice

“…23 2D IR spectroscopy 24-28 monitors the local structure and dynamics of the hydrogen bonds in water through the frequency of the hydroxyl stretch vibration. [29][30][31][32] We demonstrated that the high structural disorder of LDA on the one hand, and the complete lack of spectral diffusion on the other hand, allow one to observe how various spectral properties of the hydroxyl a) phamm@pci.uzh.ch stretch vibration varies with hydrogen bond strength to the water molecules in the first coordination shell.…”

“…This procedure separates vibrational (anisotropic) from thermal (isotropic) signals by exploiting the lack of orientation motion in the ice samples. 23 The on-diagonal (blue) peaks are associated with bleach and stimulated emission between ground and first excited state (0-1 transition), while the oppositely signed off-diagonal peaks (red) are due to the anharmonically shifted absorption from the first to the second excited state (1-2 transition). For all three samples, the lineshapes of 0-1 transition are consistent in terms of bandwidth and position with the corresponding absorption spectra (Fig.…”

Transient Glass Formation around a Quadrupolar Photoexcited Dye in a Strongly H‐Bonding Liquid Observed by Transient 2D‐IR Spectroscopy

“…This absence of spectral diffusion indicates that the environment of the tight complex is static on the timescale of typical fluctuations of this solvent and resembles that of ag lass. [15] Similarly slow spectral diffusion has only been reported for ionic liquids. [16] Asubstantial slowing down of the translational dynamics of water has also been observed in the solvation shell of different solutes.…”