Raman scattering from fluid hydrogen to 2500 amagats

Ne, Moulton; Gh, Watson; Wb, Daniels; Dm, Brown

doi:10.1103/physreva.37.2475

Cited by 20 publications

(12 citation statements)

References 24 publications

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“…11,14 -16 In this paper, we have presented only qualitative data on shifts by way of Figs 1 and 3. The Q-branch behavior is only partially similar to the higher density self-broadening in H 2 observed by Moulton et al 6 They observed the coalescence of the Q(0), Q(1) and Q (2) lines, but at much higher densities, and they did not see a measurable shift in any of the Q-branch lines until the density was well above 500 amagat. The Q-branch behavior is only partially similar to the higher density self-broadening in H 2 observed by Moulton et al 6 They observed the coalescence of the Q(0), Q(1) and Q (2) lines, but at much higher densities, and they did not see a measurable shift in any of the Q-branch lines until the density was well above 500 amagat.…”

Section: Line Shiftssupporting

confidence: 78%

Hydrogen Raman linewidths in supercritical water and carbon dioxide

Rice

Wickham

2000

J. Raman Spectrosc.

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H2 Raman linewidths provide a probe of intermolecular potentials and have been examined in the past to explore collisional dynamic characteristics in high‐pressure gas mixtures. We report the measurement of H2 Δv = 1 Q‐branch lines, Q(0)– Q(5), and pure rotational lines, S(0)– S(5), in supercritical water and high‐pressure carbon dioxide at 450 °C and pressures up to 50 MPa. The data are analyzed by separating the contributions to the line broadening due to different collisional processes characterized as vibrational dephasing, inelastic J‐changing and rotational reorientation. The linear broadening coefficients for these different processes are determined. Both water and carbon dioxide are shown to be much more effective at disturbing H2 rotation than other less polar molecules that have been examined in the past. Water is shown to be much more effective at causing inelastic J‐changing relaxation than carbon dioxide. Elastic rotational reorientation rates are comparable for both colliders. Copyright © 2000 John Wiley & Sons, Ltd.

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Section: Line Shiftssupporting

confidence: 78%

Hydrogen Raman linewidths in supercritical water and carbon dioxide

Rice

Wickham

2000

J. Raman Spectrosc.

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“…In the fluid at room temperature, the internuclear distance has been determined by Moulton et al,2 up to a density of about 60 mol/l, extending the previous result by May et al 3 Few authors have attempted the determination of this same quantity from spectroscopic measurements in the solid. 4,5 In one case, 5 this analysis has produced inconsistent results.…”

supporting

confidence: 61%

“…͑2͔͒, that is, the experimentally accessible estimate of the hydrogen molecule internuclear distance. The value of r m thus obtained, together with the results of Moulton et al 2 and those of May et al, 3 is plotted as a function of density in Fig. 3.…”

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confidence: 67%

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Molecular hydrogen internuclear distance in high-pressure fluid and solid phases at room temperature

Ulivi¹,

Zoppi²,

Gioè

et al. 1998

Phys. Rev. B

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Pure rotational Raman-scattering spectra have been measured in fluid and solid hydrogen at room temperature and at pressures from 0.3 to 20 GPa. The frequency position of the four molecular rotational lines S 0 (0), S 0 (1), S 0 (2), S 0 (3) has been determined as a function of pressure. The analysis of these data has permitted the extraction of the density dependence of the hydrogen internuclear distance. In the fluid phase, this quantity shows a marked decrease in the density range from 50 mol/l to the freezing transition, with a negative curvature. In the solid phase the slope changes markedly, becoming less negative, while the curvature becomes slightly positive.

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“…As expected, the S 0 -branch of hydrogen at 557 cm –1 overlaps with the bending mode of urea. Moulton et al 30 showed that the vibrational modes of hydrogen are shifted up to 4.6 GPa. However, according to our spectra, the vibration modes belong to Q 1 (2), and Q 1 (3)-branch disappeared when hydrogen molecules entered the urea channel pores above 0.36 GPa ( Figure 4 b), which can be due to interactions between hydrogen and urea molecules.…”

Section: Results and Discussionmentioning

confidence: 99%

High-Pressure Sorption of Hydrogen in Urea

2021

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Hydrogen sorption in urea C(NH 2 ) 2 O has been probed by direct measurements in Sievert’s apparatus at 7.23 and 11.12 MPa as well as by Raman spectroscopy for the sample compressed and heated in a high-pressure gas-loaded diamond-anvil cell up to 14 GPa. Both these methods consistently indicate the occurrence of small nonstoichiometric sorption of hydrogen in urea phase I. The compression of urea in hydrogen affects the Raman shifts of the C–N bending mode δ and the stretching mode υ s . The sorption affects the H 2 vibron position too. The sorption of 1.3 × 10 –2 at 11.12 MPa corresponds to a stochastic distribution of H 2 molecules in channel pores of urea. The mechanism leading to this stochastic sorption involves strong correlations between the swollen nanodot regions around the pores accommodating H 2 molecules and the squeezed neighboring pores too narrow to act as possible sorption sites. This study on the hydrogen-bonded framework (HOF) of urea marks the smallest pores capable of absorbing hydrogen documented so far. This observation also reveals a new class of compounds, which is located between those that absorb large stoichiometric amounts of certain guest molecules and those that do not absorb them at all, namely, the group of compounds that absorb the guests in a stochastic manner.

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Raman scattering from fluid hydrogen to 2500 amagats

Cited by 20 publications

References 24 publications

Hydrogen Raman linewidths in supercritical water and carbon dioxide

Hydrogen Raman linewidths in supercritical water and carbon dioxide

Molecular hydrogen internuclear distance in high-pressure fluid and solid phases at room temperature

High-Pressure Sorption of Hydrogen in Urea

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