Mechanism for vibrational relaxation in water investigated by femtosecond infrared spectroscopy (original) (raw)
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Physical Review Letters, 2009
Vibrational energy relaxation of the NH-, OH-, and OD-stretching modes in hydrogen-bonded liquids has been investigated by means of infrared pump-probe spectroscopy. The relaxation rates have been determined both in neat liquids and in isotopic mixtures with systematically varied isotope fractions. In all liquids, the vibrational relaxation rate increases as the isotope fraction is increased and reaches a maximum in the neat liquid. The dependence of the relaxation rate on the isotope fraction suggests a relaxation channel in which the vibrational energy is partitioned between accepting modes of two neighboring molecules.
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.
Ultrafast vibrational energy relaxation of the water bridge
Physical chemistry chemical physics : PCCP, 2012
We report the energy relaxation of the OH stretch vibration of HDO molecules contained in an HDO:D(2)O water bridge using femtosecond mid-infrared pump-probe spectroscopy. We found that the vibrational lifetime is shorter (~630 ± 50 fs) than for HDO molecules in bulk HDO:D(2)O (~740 ± 40 fs). In contrast, the thermalization dynamics following the vibrational relaxation are much slower (~1.5 ± 0.4 ps) than in bulk HDO:D(2)O (~250 ± 90 fs). These differences in energy relaxation dynamics strongly indicate that the water bridge and bulk water differ on a molecular scale.
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.
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.
On the orientational relaxation of HDO in liquid water
The Journal of Chemical Physics, 2005
We use femtosecond mid-infrared pump-probe spectroscopy to study the orientational relaxation of HDO molecules dissolved in H 2 O. In order to obtain a reliable anisotropy decay we model the effects of heating and correct for these effects. We have measured the reorientation time constant of the OD vibration from 2430 to 2600 cm −1 , and observe a value of 2.5 ps that shows no variation over this frequency interval. Our results are discussed in the context of previous experiments that have been performed on the complementary system of HDO dissolved in D 2 O.
Transient absorption of vibrationally excited water
The Journal of Chemical Physics, 2002
We study the spectral response of the transition between the first and the second excited state of the O-H stretch vibration of HDO dissolved in liquid D 2 O with two-color femtosecond mid-infrared spectroscopy. The spectral response of this transition differs strongly from the fundamental absorption spectrum of the O-H stretch vibration. In addition, excitation of the O-H stretch vibration is observed to lead to a change of the hydrogen-bond dynamics of liquid water. We show that both these observations can be described with a refined quantum-mechanical version of the Lippincott-Schroeder model for hydrogen-bonded OH¯O systems.
Vibrational Relaxation of the Bending Mode of HDO in Liquid D 2 O
The Journal of Physical Chemistry A, 2005
The vibrational relaxation of the bending mode of HDO in liquid D 2 O has been studied using time-resolved mid-infrared pump-probe spectroscopy. At short delays, the transient spectrum clearly shows the V ) 1 f 2 induced absorption and V ) 1 f 0 bleaching and stimulated emission, whereas at long delays, the transient spectrum is dominated by the spectral changes caused by the temperature increase in the sample after vibrational relaxation. From the decay of the V ) 1 f 2 induced absorption, we obtain an estimate of 390 ( 50 fs for the vibrational lifetime, in surprisingly good agreement with recent theoretical predictions. In the V ) 0 f 1 frequency region, the decay of the absorption change involves a second, slower component, which suggests that after vibrational relaxation the system is not yet in thermal equilibrium.