Terahertz absorption spectra of supercritical CHF3 to investigate local structure through rotational and hindered rotational motions

Saitow, Ken−ichi; Ohtake, Hideyuki; Sarukura, Nobuhiko; Nishikawa, Keiko

doi:10.1016/s0009-2614(01)00467-5

Cited by 41 publications

(49 citation statements)

References 26 publications

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“…One of our motivations to perform this analysis was a previous debate in literature concerning the experimental observation of the local density augmentation in supercritical fluoroform. Saitow et al [66][67][68][69] performed spectroscopic measurements of pure supercritical fluoroform and methanol. According to their experiments, the local density augmentation in methanol is more pronounced than in fluoroform.…”

Section: -5mentioning

confidence: 99%

“…Song and Maroncelli 62 systematically examined the disagreement between their simulation and experiment in the case of supercritical fluoroform. In that paper Song and Maroncelli pointed out that a possible reason for this discrepancy could be the assumption of a linear proportionality between spectral shifts and local densities as well as the methodology employed to derive local densities from the Raman shifts observed by Saitow et al 67 In general, several recent studies have provided information about the density dependence of spectroscopic observables 24,33,34,62,[71][72][73] in supercritical fluids. From these studies we may see that, in general, there is a nonlinear bulk density dependence; however the relation between these spectroscopic observables with the local density is still not very clear.…”

Section: -5mentioning

confidence: 99%

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Effect of the local hydrogen bonding network on the reorientational and translational dynamics in supercritical water

Skarmoutsos

Guàrdia

2010

The Journal of Chemical Physics

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Molecular dynamics simulations have been performed in a wide range of densities along a near critical isotherm of supercritical water in order to reveal the interconnection between the local hydrogen bonding ͑HB͒ network and several related dynamic properties. The results obtained have revealed a significant slowing down of reorientational dynamics of the water molecules as the value of the number of hydrogen bond per molecule increases and this is reflected on the increase in the reorientational correlation times. The calculated reorientational times exhibit also an increasing trend by increasing the bulk density, and this effect is more pronounced in the case of the first-order Legendre reorientational correlation functions. A clear nonlinear dependence of the librational mode frequencies of the water molecules on the augmented local density around them has also been revealed. This result could be regarded as an additional support of experimental observations suggesting the use of a nonlinear relation when analyzing the density dependence of spectroscopic peak frequencies in order to extract information about local density augmentation in supercritical fluids. The HB dynamics have been also investigated, revealing a plateau in the calculated HB lifetimes at intermediate and higher liquidlike densities and a small increase at low, gaslike densities.

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Section: -5mentioning

confidence: 99%

Section: -5mentioning

confidence: 99%

Effect of the local hydrogen bonding network on the reorientational and translational dynamics in supercritical water

Skarmoutsos

Guàrdia

2010

The Journal of Chemical Physics

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“…In our previous study of THz absorption spectra for supercritical CHF 3 , rotational spectra shift toward the higher energy side as density increases. 19 In the time domain, the obtained time correlation function describing rotational motions decays within a few hundred femtoseconds, and the motion becomes faster near r ϭ1. 30 For the same pure fluid studied by polarized vibrational Raman spectra and MD simulation 31 and nuclear magnetic resonance, 32 rotational relaxation times show similar features, which indicate minimum near r ϭ1.…”

Section: B Relationship Between Critical Slowing Down Of Density Flumentioning

confidence: 94%

“…1͑a͒. From the point of view on local structure around the nearest neighbors of a molecule, both measurements of terahertz ͑THz͒ absorption spectra for rotational motions 19 and spontaneous vibrational Raman spectra 20 imply that the ridge behaves as a trace of the gas-liquid coexistence curve in supercritical region where the short-range structure changes from gas-like to liquid-like in terms of molecular aggregations. Autocorrelation functions describing local density dynamics for neat Lennard-Jones fluid have recently been investigated by twodimensional molecular dynamics simulations near thermodynamic states giving the most inhomogeneous structure.…”

Section: Introductionmentioning

confidence: 99%

Correlation time of density fluctuation for supercritical ethylene studied by dynamic light scattering

Saitow

Ochiai

Kato

et al. 2002

The Journal of Chemical Physics

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Time dependence of density fluctuation for neat supercritical ethylene (C 2 H 4 ) is investigated by dynamic light scattering at various densities in isothermal conditions of reduced temperatures T r ϭT/T c ϭ1.02, 1.04, and 1.06. Time correlations of the density fluctuation for all thermodynamic states decay as single exponential functions with the time constant of submicrosecond. Critical slowing down of diffusive motions is observed in the time domain, and the correlation time of the density fluctuation becomes maximum at the extension of the gas-liquid coexistence curve on the P -T phase diagram. It is revealed that the time dependence of the density fluctuation just corresponds to the magnitude of static density fluctuation obtained by small-angle x-ray scattering measurements. By measuring correlation times as a function of scattering angle, the critical slowing down is thermodynamically discussed. It is elucidated experimentally that the critical slowing down of diffusive motions considerably correlates to the increase of specific heat capacity, the decrease of the thermal diffusivity, and rotational relaxation time in the supercritical state of the neat fluid.

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“…This relatively "new" type of radiation can be used for physicochemical analysis of materials, ecography and tomography of tissues in medical research, monitoring of the Earth's atmosphere, etc. [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Generation and detection of ultrashort pulses of electromagnetic field in the terahertz range and their application for spectroscopy

Ахмеджанов

Korytin

Litvak

et al. 2005

Radiophys Quantum Electron

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We present experimental results on generation of pulsed terahertz radiation in a ZnTe crystal using nonlinear optical rectification of high-power femtosecond laser pulses. The use of terahertz pulses for spectroscopy is tested in the rotational lines of absorption of water vapors in the atmosphere. Panoramic spectra of absorption of a number of solvents and protein solutions are measured in the range from 0.2 to 2 THz.

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Terahertz absorption spectra of supercritical CHF3 to investigate local structure through rotational and hindered rotational motions

Cited by 41 publications

References 26 publications

Effect of the local hydrogen bonding network on the reorientational and translational dynamics in supercritical water

Effect of the local hydrogen bonding network on the reorientational and translational dynamics in supercritical water

Correlation time of density fluctuation for supercritical ethylene studied by dynamic light scattering

Generation and detection of ultrashort pulses of electromagnetic field in the terahertz range and their application for spectroscopy

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