Evidence for Cooperative Vibrational Relaxation of the NH-, OH-, and OD-Stretching Modes in Hydrogen-Bonded Liquids Using Infrared Pump-Probe Spectroscopy (original) (raw)
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Mechanism for vibrational relaxation in water investigated by femtosecond infrared spectroscopy
The Journal of Chemical Physics, 1999
We present a study on the relaxation of the O-H stretch vibration in a dilute HDO:D 2 O solution using femtosecond mid-infrared pump-probe spectroscopy. We performed one-color experiments in which the 0→1 vibrational transition is probed at different frequencies, and two-color experiments in which the 1→2 transition is probed. In the one-color experiments, it is observed that the relaxation is faster at the blue side than at the center of the absorption band. Furthermore, it is observed that the vibrational relaxation time T 1 shows an anomalous temperature dependence and increases from 0.74Ϯ0.01 ps at 298 K to 0.90Ϯ0.02 ps at 363 K. These results indicate that the O-H¯O hydrogen bond forms the dominant accepting mode in the vibrational relaxation of the O-H stretch vibration.
Vibrational Relaxation and Hydrogen-Bond Dynamics of HDO:H 2 O
The Journal of Physical Chemistry A, 2001
Femtosecond two-color mid-infrared pump-probe spectroscopy is used to study the vibrational relaxation and the hydrogen-bond dynamics of HDO dissolved in liquid H 2 O. By looking at the spectral dynamics of the OD stretch mode, direct information on the hydrogen-bond dynamics of the H 2 O solvent is obtained. By fitting the data using the Brownian oscillator model, we determined the vibrational lifetime of the OD stretch vibration and the hydrogen-bond length correlation time. The hydrogen-bond correlation time of H 2 O is significantly shorter than for D 2 O, found previously.
Vibrational relaxation of the H[sub 2]O bending mode in liquid water
The Journal of Chemical Physics, 2004
We have studied the vibrational relaxation of the H 2 O bending mode in an H 2 O:HDO:D 2 O isotopic mixture using infrared pump-probe spectroscopy. The transient spectrum and its delay dependence reveal an anharmonic shift of 55Ϯ10 cm Ϫ1 for the H 2 O bending mode, and a value of 400 Ϯ30 fs for its vibrational lifetime.
Vibrational energy relaxation pathways of water
Chemical Physics Letters, 2003
Vibrational energy relaxation (VR) of the OH stretch m OH and bend d H 2 O in water is studied by the mid-IR pump with anti-Stokes Raman probe technique. The broad m OH band in water consists of two inhomogeneously broadened subbands. VR in the larger red-shifted subband m R OH , with T 1 ¼ 0:55 ps, is shown to occur by the mechanism m OH ! d H 2 O (1/3) and m OH ! ground state (2/3). VR in the smaller longer-lived blue-shifted subband m B OH , with T 1 ¼ 0:75 ps, occurs by the mechanism m OH ! ground state. The bending fundamental d H 2 O decays directly to the ground state with T 1 ¼ 1:4 ps.
Coherent Response of Hydrogen Bonds in Liquids Probed by Ultrafast Vibrational Spectroscopy
The Journal of Physical Chemistry A, 2001
We report the first observation of coherent vibrational dynamics in a hydrogen bond obtained by femtosecond nonlinear measurements in the mid-infrared spectral range. The results provide the first experimental evidence in the time domain for the anharmonic coupling of slow and fast vibrational motions in a hydrogen bond. We show that the absorption band of the high-frequency hydrogen stretching (O-H/O-D) vibration is modulated by a coherent oscillatory motion corresponding to a periodic variation of the hydrogen bond length and its strength. This mechanism, which is of general relevance for hydrogen bonds, is connected with underdamped low-frequency vibrationssin contrast to the assumption of overdamped nuclear motions in most theoretical treatments.
The journal of physical chemistry. A, 2015
A quantitative investigation of the relaxation dynamics of higher-lying vibrational states is afforded by a novel method of infrared pump-repump-probe spectroscopy. The technique is used to study the dynamics of OH stretching overtones in NaClO4·HDO monohydrate. We observe a continuous decrease of the energy separation for the first four states, i.e. v01 = 3575 cm(-1), v12 = 3370 cm(-1), and v23 = 3170 cm(-1), respectively. The population lifetime of the first excited state is 7.2 ps, while the one of the second excited state is largely reduced to 1.4 ps. The relaxation of the v = 2 state proceeds nearly quantitatively to the v = 1 state. The new information on the OH stretching overtones demands improved theoretical potentials and modeling of the H bond interactions. This work shows the potential of the new technique for the precise study of complex vibrational relaxation pathways.
The Journal of Chemical Physics, 2008
The pressure and temperature-dependent linear absorption spectrum of partially deuterated water HOD dissolved in heavy water D 2 O was measured in the OH-stretching spectral region. The temperature was varied in the interval of 298 K ഛ T ഛ 700 K while the density was changed within the range of 12 mol/ l ഛ ഛ 58 mol/ l corresponding to the liquid and the supercritical phases of the fluid solution. The spectra were analyzed in terms of the temperature and density dependent frequency of maximal absorbance max ͑T , ͒ and their full widths at half maximum ⌬͑T , ͒. In parallel, molecular dynamics simulations of the fluid solution were carried out to obtain the average nearest neighbor O-O distance ͗r OO ͑1͒ ͑͘T , ͒ and its dispersion ͗⌬r OO ͑1͒ ͑͘T , ͒ at any state point ͑T , ͒ for which an absorption spectrum was recorded. A correlation is presented between the experimental spectroscopic quantities max ͑T , ͒ and ⌬͑T , ͒ on the one hand and the local structural quantities ͗r OO ͑1͒ ͑͘T , ͒ and ͗⌬r OO ͑1͒ ͑͘T , ͒ on the other. This intuitive correlation can be used as a critical test for future perturbational simulations of the OH-stretching frequency shifts with hydrogen-bond geometry. Finally, a connection is made to the average hydrogen-bond connectivity in the fluid via the temperature and density dependent dielectric constant of water.
Vibrational energy relaxation of the ND-stretching vibration of NH2D in liquid NH3
Physical Chemistry Chemical Physics, 2012
The vibrational energy relaxation from the first excited ND-stretching mode of NH 2 D dissolved in liquid NH 3 is studied using molecular dynamics simulations. The rate constants for inter-and intramolecular energy transfer are calculated in the framework of the quantum-classical Landau-Teller theory. At 273 K and an ammonia density of 0.642 g cm À3 the calculated ND-stretch lifetime of t = 9.1 ps is in good agreement with the experimental value of 8.6 ps. The main relaxation channel accounting for 52% of the energy transfer involves an intramolecular transition to the first excited state of the umbrella mode. The energy difference between both states is taken up by the near-resonant bending vibrations of the solvent. Less important for the ND-stretch lifetime are both the direct transition to the ground state and intramolecular relaxation via the NH 2 D bending modes contributing 23% each. Our calculations imply that the experimentally observed weak density dependence of t is caused by detuning the resonance between the ND-stretch-umbrella energy gap and the solvent accepting modes which counteracts the expected linear increase of the relaxation rate with density.
The Journal of Physical Chemistry A
A quantitative investigation of the relaxation dynamics of higher-lying vibrational states is afforded by a novel method of infrared pump−repump−probe spectroscopy. The technique is used to study the dynamics of OH stretching overtones in NaClO 4 •HDO monohydrate. We observe a continuous decrease of the energy separation for the first four states, i.e. v 01 = 3575 cm −1 , v 12 = 3370 cm −1 , and v 23 = 3170 cm −1 , respectively. The population lifetime of the first excited state is 7.2 ps, while the one of the second excited state is largely reduced to 1.4 ps. The relaxation of the v = 2 state proceeds nearly quantitatively to the v = 1 state. The new information on the OH stretching overtones demands improved theoretical potentials and modeling of the H bond interactions. This work shows the potential of the new technique for the precise study of complex vibrational relaxation pathways.