Quantum Beats and Coherence Decay in Degenerate States Split by Solvation

Chuntonov, Lev; Kuroda, Daniel G.; Ghosh, Ayanjeet; Ma, Jianqiang; Hochstrasser, Robin M.

doi:10.1021/jz400826a

Cited by 12 publications

(11 citation statements)

References 49 publications

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“…34 Although the localized vibrational transition describes correctly the non-linear response of HDO bend, it appears that the vibrational experimental data of H 2 O is not well characterized by a localized vibrational transition. Firstly, the anisotropy of the transient grating signal 44 of the H 2 O bend shows a fast decay (see ESI†). Secondly, there is a significant change in the central frequency of the positive peak in the 2D-IR spectrum (red peak of Figure 2) during the first 0.5 ps of waiting time in H 2 O. Thirdly, it appears that at T w = 0.2 ps the 2D-IR spectrum of water contains a cross-peak (dash circle in Figure 2).…”

Section: Discussionmentioning

confidence: 99%

Non-linear infrared spectroscopy of the water bending mode: direct experimental evidence of hydration shell reorganization?

Chuntonov

Kumar

Kuroda

2014

Phys. Chem. Chem. Phys.

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The structure and dynamics of liquid water are further studied by investigating the bend vibrational mode of HDO/D2O and pure H2O via two-dimensional infrared spectroscopy (2D-IR) and linear absorption. The experimental findings and theoretical calculations support a picture in which the HDO bend is localized and the H2O bend is delocalized. The HDO and H2O bends present a loss of the frequency-frequency correlation in subpicosecond time scale. While the loss of correlation for the H2O bend is likely to be associated with the vibrational dynamics of a delocalized transition, the loss of the correlation in the localized HDO bend appears to arise from the fluctuations/rearrangements of the local environment. Interestingly, analysis of the HDO 2D-IR spectra shows the presence of multiple overlapping inhomogeneous distributions of frequencies that interchange in a few picoseconds. Theoretical calculations allow us to propose an atomistic model of the observed vibrational dynamics in which the different in homogeneous distributions and their interchange are assigned to water molecules with different hydrogen-bond states undergoing chemical exchange. The frequency shifts as well as the concentration of the water molecules with single and double hydrogen-bonds as donors derived from the theory are in good agreement with our experimental findings.

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Section: Discussionmentioning

confidence: 99%

Non-linear infrared spectroscopy of the water bending mode: direct experimental evidence of hydration shell reorganization?

Chuntonov

Kumar

Kuroda

2014

Phys. Chem. Chem. Phys.

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“…Polarization of the electric field of each pulse was controlled independently with a combination of zero-order waveplates (Karl Lambrecht) and polarizers (Specac) placed as a last optical element before the sample to avoid any potential depolarization of light upon reflection. 36–37 In the pump-probe experiments the intensity of the probe pulse was attenuated to 5% of the pump pulse intensity. The signal was collected on a 64 elements liquid nitrogen-cooled MCT array detector (Infrared Associates) coupled to a spectrograph equipped with a 50 gr/mm grating.…”

Section: Methodsmentioning

confidence: 99%

Kinetics of Exchange between Zero-, One-, and Two-Hydrogen-Bonded States of Methyl and Ethyl Acetate in Methanol

Chuntonov

Pazos

et al. 2015

J. Phys. Chem. B

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It has recently been shown that the ester carbonyl stretching vibration can be used as a sensitive probe of local electrostatic field in molecular systems. To further characterize this vibrational probe and extend its potential applications, we studied the kinetics of chemical exchange between differently hydrogen-bonded (H-bonded) ester carbonyl groups of methyl acetate (MA) and ethyl acetate (EA) in methanol. We found that while both MA and EA can form zero, one, or two H-bonds with the solvent, the population of the 2hb state in MA is significantly smaller than that in EA. Using a combination of linear and non-linear infrared measurements and numerical simulations, we further determined the rate constants for the exchange between these differently H-bonded states. We found that for MA the chemical exchange reaction between the two dominant states (i.e., 0hb and 1hb states) has a relaxation rate constant of 0.14 ps−1, whereas for EA the three-state chemical exchange reaction occurs in a predominantly sequential manner with the following relaxation rate constants: 0.11 ps−1 for exchange between 0hb and 1hb states, 0.12 ps−1 for exchange between 1hb and 2hb states.

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“…The polarization of each of the pulse is set by a polarizer before the sample. 27 The photon echo signal in the phase matching direction (−k 1 + k 2 + k 3 ) is heterodyned with a fourth IR pulse (LO) and detected with a liquid nitrogen cooled 64 element MCT array detector after dispersion in a monochromator (50 grooves/mm). In all the experiments, the LO pulses preceded the signal field by ∼1 ps.…”

Section: D Ir Spectroscopymentioning

confidence: 99%

Hydration and vibrational dynamics of betaine (N,N,N-trimethylglycine)

Cui

Mathaga

et al. 2015

The Journal of Chemical Physics

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Zwitterions are naturally occurring molecules that have a positive and a negative charge group in its structure and are of great importance in many areas of science. Here, the vibrational and hydration dynamics of the zwitterionic system betaine (N,N,N-trimethylglycine) is reported. The linear infrared spectrum of aqueous betaine exhibits an asymmetric band in the 1550-1700 cm −1 region of the spectrum. This band is attributed to the carboxylate asymmetric stretch of betaine. The potential of mean force computed from ab initio molecular dynamic simulations confirms that the two observed transitions of the linear spectrum are related to two different betaine conformers present in solution. A model of the experimental data using non-linear response theory agrees very well with a vibrational model comprising of two vibrational transitions. In addition, our modeling shows that spectral parameters such as the slope of the zeroth contour plot and central line slope are both sensitive to the presence of overlapping transitions. The vibrational dynamics of the system reveals an ultrafast decay of the vibrational population relaxation as well as the correlation of frequency-frequency correlation function (FFCF). A decay of ∼0.5 ps is observed for the FFCF correlation time and is attributed to the frequency fluctuations caused by the motions of water molecules in the solvation shell. The comparison of the experimental observations with simulations of the FFCF from ab initio molecular dynamics and a density functional theory frequency map shows a very good agreement corroborating the correct characterization and assignment of the derived parameters. C 2015 AIP Publishing LLC. [http://dx

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Quantum Beats and Coherence Decay in Degenerate States Split by Solvation

Cited by 12 publications

References 49 publications

Non-linear infrared spectroscopy of the water bending mode: direct experimental evidence of hydration shell reorganization?

Non-linear infrared spectroscopy of the water bending mode: direct experimental evidence of hydration shell reorganization?

Kinetics of Exchange between Zero-, One-, and Two-Hydrogen-Bonded States of Methyl and Ethyl Acetate in Methanol

Hydration and vibrational dynamics of betaine (N,N,N-trimethylglycine)

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