Three-dimensional infrared spectroscopy of isotope-diluted ice Ih

Abstract

Using three-dimensional infrared (3D-IR) spectroscopy, we investigate the vibrational dynamics of isotope-diluted ice Ih. By probing the OD stretch mode of HOD in H2O, we observe an extremely rapid decay ( 200 fs) of the population from the second vibrational excited state. Quantum simulations based on a two-dimensional Lippincott-Schroeder potential agree nearly quantitatively with the experimental 3D-IR lineshapes and dynamics. The model suggests that energy dissipation is enhanced due to nonadiabatic effects between vibrational states, which arise from strong mode-mixing between the OD stretch mode with lattice degrees of freedom. Furthermore, we compare the simulation results to ab-initio based potentials, in which the hydrogen bond anharmonicity is too small to reproduce the experimental 3D-IR spectra. We thus conclude that the Lippincott-Schroeder potential effectively coalesces many degrees of freedom of the crystal into one intermolecular coordinate. Three-dimensional infrared spectroscopy of isotope-diluted ice IhFivos Perakis, Joanna A. Borek and Peter Hamm Physikalisch-Chemisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland, phamm@pci.uzh.ch (Dated: June 14, 2013) Using three-dimensional infrared (3D-IR) spectroscopy, we investigate the vibrational dynamics of isotope-diluted ice Ih. By probing the OD stretch mode of HOD in H2O, we observe an extremely rapid decay (≈200 fs) of the population from the second vibrational excited state. Quantum simulations based on a two-dimensional Lippincott-Schroeder potential agree nearly quantitatively with the experimental 3D-IR lineshapes and dynamics. The model suggests that energy dissipation is enhanced due to nonadiabatic effects between vibrational states, which arise from strong mode-mixing between the OD stretch mode with lattice degrees of freedom. Furthermore, we compare the simulation results to ab-initio based potentials, in which the hydrogen bond anharmonicity is too small to reproduce the experimental 3D-IR spectra. We thus conclude that the Lippincott-Schroeder potential effectively coalesces many degrees of freedom of the crystal into one intermolecular coordinate.

Nonadiabatic vibrational dynamics in the HCO2−⋅H2O complex

“…The time scales are quite typical for the relaxation of a vibrational mode. [13][14][15] Fig . 6 shows the time evolution of kinetic energy of the low-frequency vibrations in the |0, 0, 0⟩ ground state.…”

“…Furthermore, if a hydrogen bond is of intramolecular nature, [6][7][8] binding a dimer with reasonably well defined structure, 9,10 or in hydrogen-bonded molecular crystals, 11,12 the vibrational band often contains a pronounced substructure. The nonlinear pump-probe response of these infrared (IR) transitions, in turn, often decays on an ultrafast (a few 100 fs) time scale [13][14][15] and in some cases also exhibits complex oscillatory features. [6][7][8][9][10][11][12] It is the very anharmonic nature of the hydrogen bond potentials that gives rise to the peculiar vibrational spectroscopy, [16][17][18][19][20][21][22] i.e., in essence the fact that the typical dissociation energy of a hydrogen bond is in the same range as the frequency of its vibrational modes.…”

Fully absorptive 3D IR spectroscopy using a dual mid-infrared pulse shaper

“…Their data helped reveal evidence for heterogeneous structural dynamics in isotope substituted liquid water 20 and recently in ice. 21 The method presented in this paper is conceptually the most similar to the one presented in Refs. 11, 20, and 21, namely, we present fifth-order based fully absorptive 3D IR spectroscopy.…”

“…All the peaks in the 3D IR spectra of W(CO) 6 can be similarly assigned to one or more Feynman pathways. We note that there is a peak expected at ω 1 = ω 01 , ω 3 = ω 21 , and ω 5 = ω 01 theoretically which is absent in the full timedomain and mixed time-and frequency-domain spectra but is present in the full frequency-domain spectra ( Fig. 8(b) peak at ω 1 /2π = 1983 cm −1 , ω 3 /2π = 1970 cm −1 ).…”

“…In principle it is possible to do 3D IR experiments at lower pump intensity to minimize such effects, while still retaining enough power to generate fifth-order signal, but we have not pursued that in this work. It is interesting to note that this peak was also unexpectedly weak in the 3D IR spectra of water and ice, 20,21 suggesting that its intensity may be especially dependent on vibrational dynamics.…”