Self Diffusion in Carbon Dioxide Near the Critical Point

Krynicki, K.; Meragi, A.‐L.; Powles, J.G.

doi:10.1002/bbpc.19810851215

Cited by 20 publications

(8 citation statements)

References 15 publications

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“…The diffusion coefficient for liquid carbon dioxide at 30.5°C is ¾5 ð 10 4 cm 2 /s. 15 Therefore, the average displacement of a single molecule during the dephasing time T 2 (¾3 ps) is about 0.2 nm. This value is much less than the NG pore diameter (4 nm).…”

Section: Resultsmentioning

confidence: 99%

Vibrational line shapes of liquid and subcritical carbon dioxide in nano‐pores

Arakcheev

Баграташвили

Dubyanskiy

et al. 2008

J Raman Spectroscopy

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Coherent anti-Stokes Raman spectroscopy (CARS) spectra of the Fermi-dyad n 1 /2n 2 Q-branches were recorded in subcritical (T = 30.5°C) carbon dioxide imbedded in a nano-porous glass (NG) matrix with pore size of 4 nm and in bulk. The spectral broadening of liquid carbon dioxide confined inside the pores is essentially not homogeneous in contrast to the case of the unconfined one. Analysis shows that the spectral line shape is defined by two resonant contributions provided by the core bulk molecules and those near the surface layer inside the NG pores as well as by nonresonant contributions of the glass matrix. The spectrum attributed to the molecules from near-surface layer has several times greater linewidth and is shifted to the low-wavenumber side in comparison with the spectrum in the bulk.

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Section: Resultsmentioning

confidence: 99%

Vibrational line shapes of liquid and subcritical carbon dioxide in nano‐pores

Arakcheev

Баграташвили

Dubyanskiy

et al. 2008

J Raman Spectroscopy

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“…The self-part of the dynamic structure factor is approximated to be purely diffusive, where D means the self-diffusion coefficient of the solute. We neglect the critical anomaly of the self-diffusion coefficient, because it is quite small if any. , …”

Section: Resultsmentioning

confidence: 99%

“…We neglect the critical anomaly of the self-diffusion coefficient, because it is quite small if any. 31,32 Equations 20 and 21 are substituted into eq 19 to get the final expression as follows:…”

Section: Iiia Static Fluctuationmentioning

confidence: 99%

Study of Nonpolar Solvation Dynamics in Supercritical Lennard−Jones Fluids in Terms of the Solvent Dynamic Structure Factor

2002

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The nonpolar solvation dynamics in Lennard−Jones fluids is discussed in terms of the relationship with the dynamic structure factor of neat solvent, using the theoretical expression that describes the solvation correlation function as the superposition of solvent dynamic structure factors at various wavenumbers. Several expressions for the coupling strength between the state transition of the solute and the solvent density modes are examined with respect to their abilities to predict the static fluctuation. In the present theoretical model, it is found that the difference between the ground- and excited-state solute−solvent interactions can be adequately taken as the coupling strength with the solvent density mode. Employing this expression for the coupling, the solvent fluctuation around k ≅ σ -1 (σ stands for the diameter of the solvent) contributes dominantly to the static fluctuation in all the densities investigated. This corresponds to the feature of the solvation dynamics in mixed solvents, in which the effective wavenumber is determined to be 1.14σ-1 from the proportionality between the solvation rates and the diffusion coefficients in the higher-density region. The half decay time (t 1/2) of the dynamic structure factor at this wavenumber shows similar density dependence to that of the solvation correlation function obtained in our previous work. The half decay time of the dynamic structure factor is correlated with the static structure factor. This supports our previous proposal that the curvature of the free energy surface along the solvation coordinate is essential to the solvation dynamics. The agreement between the present theory and the simulation is further improved by taking the motion of the solute into account.

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“…In fact, Duffield and Harris 12 reported a sudden increase of the values of D near the critical temperature. NMR studies by Krynicki et al 13 and by Etesse et al 14 stand in contradiction to the finding of Duffield and Harris and found no anomaly in the behavior of D. Although the values of D given in the two cited papers were measured by the same technique, there is a 40% systematic difference between the two studies. In general, most of the experimental results which were reviewed by Hamann et al 15 indicate that there is no anomaly in the behavior of D in the critical region of systems such as CH 4 , C 2 H 4 , CClF 3 , and SF 6 .…”

Section: Introductionmentioning

confidence: 69%

Low-frequency Raman spectra of sub- and supercritical CO2: Qualitative analysis of the diffusion coefficient behavior

Idriss

Longelin

Damay

et al. 2005

The Journal of Chemical Physics

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We report the results of the low-frequency Raman experiments on CO(2) which were carried out in a wide density range, along the liquid-gas coexistence curve in a temperature range of 293-303 K, and on the critical isochore of 94.4 cm(3) mol(-1) in a temperature range of 304-315 K. In our approach, the qualitative behavior of the diffusion coefficient D is predicted, assuming the following: first, that the low-frequency Raman spectra can be interpreted in terms of the translation rotation motions; second, that the random force could be replaced by the total force to calculate the friction coefficient; and finally, that the Einstein frequency is associated with the position of the maximum of the low-frequency Raman spectrum. The results show that the diffusion coefficient increases along the coexistence curve, and its values are almost constant on the critical isochore. The predicted values reproduce qualitatively those obtained by other techniques. The values of D were also calculated by molecular-dynamics simulation and they qualitatively reproduce the behavior of D.

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Self Diffusion in Carbon Dioxide Near the Critical Point

Cited by 20 publications

References 15 publications

Vibrational line shapes of liquid and subcritical carbon dioxide in nano‐pores

Vibrational line shapes of liquid and subcritical carbon dioxide in nano‐pores

Study of Nonpolar Solvation Dynamics in Supercritical Lennard−Jones Fluids in Terms of the Solvent Dynamic Structure Factor

Low-frequency Raman spectra of sub- and supercritical CO2: Qualitative analysis of the diffusion coefficient behavior

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