Composition of clathrate gas hydrates of chlorodifluoromethane, trichlorofluoromethane, chlorine, perchloryl fluoride, hydrogen sulfide, and sulfur hexafluoride

Cady, George H.

doi:10.1021/j150622a005

Cited by 40 publications

(39 citation statements)

References 2 publications

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“…As such, iodine does not significantly affect the stability of the parent hydrate. We also infer that I 2 does not induce any structural reorganization of the water cavities and is most likely trapped in large 5 12 6 4 cages. Figure 2 shows a slice of a space-filling model for a 5 12 6 4 cage occupied by an iodine molecule.…”

Section: Introductionmentioning

confidence: 78%

“…A Birge-Sponer fit to the energy difference between two adjacent lines, ω V+1,V , yields ω e ) 214 ( 1 cm -1 , which, within experimental error, is the same as the gas-phase value (214.5 cm -1 ). For comparison, ω e ) 212.5 and 209.6 cm -1 in CCl 4 and CHCl 3 , respectivley. 16,17 Unfortunately, we were not able to obtain a reliable anharmonicity constant, ω e x e , but it appears that ω e x e may be even less than in the gas phase, 0.6 cm -1 .…”

Section: Resultsmentioning

confidence: 99%

“…A CCD detector (Andor Technology) with a 1/4 m monochromator (Oriel) was used to disperse and detect the spectra. The 250-2000 cm -1 spectral range was calibrated with the bands of iodine in CCl 4 and was checked against the known Raman spectra of DMSO, d-choroform, and n-hexane. The uncertainty in the band positions was (1 cm -1 .…”

Section: Methodsmentioning

confidence: 99%

“…The decay rate of the iodine progression in clathrate hydrate (i.e., the integral intensity dependence of overtones on the vibrational quantum number) suggests an electronic dephasing time of ∼80 fs, as established in the analysis of the resonance Raman spectra of iodine in rare gas matrices. 32 For inert solvents such as CCl 4 or n-hexane, the resonance Raman progression can be obtained up to the 15th -to 20th overtone with a gradual, monotonic intensity decrease. 16 In contrast, in polar solvents such as p-dioxane, only a short resonance Raman progression, up to V ) 3, is observed, and the intensity of the first overtone is no more than 10% of that of the fundamental transition.…”

Section: Uv-vis Spectroscopy As Illustrated Inmentioning

confidence: 99%

“…Figure 2 shows a slice of a space-filling model for a 5 12 6 4 cage occupied by an iodine molecule. 3 , and 5 12 6 4 . Cage nomenclature is as follows: 5 and 6 stand for pentagonal and hexagonal faces, respectively, and the superscript gives the number of each face type.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic Signatures of Halogens in Clathrate Hydrate Cages. 2. Iodine

et al. 2007

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UV-vis and Raman spectroscopy were used to study iodine molecules trapped in sII clathrate hydrate structures stabilized by THF, CH 2 Cl 2 , or CHCl 3 . The spectra show that the environment for iodine inside the water cage is significantly less perturbed than either in aqueous solution or in amorphous water-ice. The resonance Raman progression of I 2 in THF clathrate hydrate can be observed up to V ) 6 when excited at 532 nm. The extracted vibrational frequency ω e ) 214 ( 1 cm -1 is the same as that of the free molecule to within experimental error. At the same time, the UV-vis absorption spectrum of I 2 in the sII hydrate exhibits a relatively large, 1440 cm -1 , blue-shift. This is mainly ascribed to the differential solvation of the I 2 electronic states. We conclude that iodine in sII hydrate resides in a 5 12 6 4 cavity, in which the ground-state I 2 potential is not significantly perturbed by the hydrate lattice. In contrast, in water and in ice, the valence absorption band of I 2 is dramatically broadened and blue-shifted by 3000 cm, and the resonance Raman scattering is effectively quenched. These observations are shown to be consistent with a strong interaction between water molecule and iodine through the lone pair of electrons on water as in the case of bromine in the same media. The results presented here, and the stability of other halogen hydrates, were used to test the predictions of simple models and force-field calculations of the host cage-guest association energy.

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Section: Introductionmentioning

confidence: 78%