Synthesis and infrared characterization of Br–HBr and Br–DBr entrance channel complexes in solid parahydrogen

Kettwich, Sharon C.; Pinelo, Laura F.; Anderson, David T.

doi:10.1039/b806276e

Cited by 20 publications

(33 citation statements)

References 47 publications

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“…5,6 They found that the jumping frequency does not depend on temperature below 7 K and concluded by performing a model calculation that the jumping occurs via quantum three-particle cyclic exchange. The same mechanism was also proposed for diffusion of 3 He in solid 4 He. 7 They also concluded that the temperature dependence between 7 and 10 K can be interpreted as migration by particle-vacancy exchange in which the vacancy is formed thermally, but moves by tunneling.…”

Section: Introductionsupporting

confidence: 50%

“…Thermal diffusion occurs via a classical pathway with activation energy and its rate shows Arrhenius-type temperature dependence. Anderson et al 4 reported that Br atoms migrate in solid pH 2 and recombine to form Br 2 molecules at 4.3 K, but not at 1.8 K. This temperature dependence indicates that diffusion of Br atoms in solid pH 2 is probably thermal. On the other hand, in quantum diffusion, particles migrate by quantum tunneling, where the rate need not show Arrhenius-type temperature dependence.…”

Section: Introductionmentioning

confidence: 92%

“…For example, related to the mechanism c, there is a theoretical proposal by Widom and Locke 24 that vacancies exist even around 0 K in quantum solids due to quantum effect. According to their report, the upper limits of the vacancy concentration in solid 4 He near 0 K is in the order of 100 ppm. This concentration is larger than that of the thermally equilibrated vacancy of ∼10 −4 ppm estimated by Eq.…”

Section: Hypothetical Mechanismmentioning

confidence: 97%

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Diffusion of hydrogen fluoride in solid parahydrogen

Ooe

Miyamoto

Kuma

et al. 2013

The Journal of Chemical Physics

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We studied diffusion of hydrogen fluoride (HF) in solid parahydrogen (pH2) around 4 K. Diffusion rates were determined from time dependence of FT-IR spectra of HF monomers. The absorption of HF monomers shows temporal decay due to dimerization reaction via diffusion. It was found that the rates are affected by the sample temperature, the initial HF concentration, and annealing of samples. The observed non-Arrhenius-type temperature dependence suggests that the diffusion is dominated by a quantum tunneling process, that is, "quantum diffusion." Deceleration of the diffusion in condensed samples and acceleration in annealed samples were also observed. These results can be attributed to the fact that lower periodicity of samples due to impurities or defects suppresses the quantum tunneling. It seems to be difficult to explain the observed dependences by three possible diffusion mechanisms, exchange of chemical bonds, direct cyclic exchange, and exchange with mobile vacancy. Therefore, we propose a hypothetical mechanism by exchange of vacancies originating from quantum effect.

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Section: Introductionsupporting

confidence: 50%

Section: Introductionmentioning

confidence: 92%

Section: Hypothetical Mechanismmentioning

confidence: 97%

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Diffusion of hydrogen fluoride in solid parahydrogen

Ooe

Miyamoto

Kuma

et al. 2013

The Journal of Chemical Physics

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“…In the course of related FTIR spectroscopic studies of the entrance channel complexes Br-HBr and Br-DBr, 28 we performed a number of 355-nm photolysis experiments on Br 2 /HBr double-doped pH 2 solids with varying initial Br 2 concentrations. Unfortunately, we did not record these FTIR spectra over the same spectral range and therefore do not have information on the intensity of the U 1 (0) transition to determine X hcp .…”

Section: Br So Transition Lineshapementioning

confidence: 99%

High-resolution infrared spectroscopy of atomic bromine in solid parahydrogen and orthodeuterium

Kettwich

Anderson

2013

The Journal of Chemical Physics

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This work extends our earlier investigation of the near-infrared absorption spectroscopy of atomic bromine (Br) trapped in solid parahydrogen (pH2) and orthodeuterium (oD2) [S. C. Kettwich, L. O. Paulson, P. L. Raston, and D. T. Anderson, J. Phys. Chem. A 112, 11153 (2008)]. We report new spectroscopic observations on a series of double transitions involving excitation of the weak Br-atom spin-orbit (SO) transition ((2)P(1/2) ← (2)P(3/2)) in concert with phonon, rotational, vibrational, and rovibrational excitation of the solid molecular hydrogen host. Further, we utilize the rapid vapor deposition technique to produce pH2 crystals with a non-equilibrium mixture of face centered cubic (fcc) and hexagonal closed packed (hcp) crystal domains in the freshly deposited solid. Gentle annealing (T = 4.3 K) of the pH2 sample irreversibly converts the higher energy fcc crystal domains to the slightly more stable hcp structure. We follow the extent of this conversion process using the intensity of the U1(0) transition of solid pH2 and correlate crystal structure changes with changes in the integrated intensity of Br-atom absorption features. Annealing the pH2 solid causes the integrated intensity of the zero-phonon Br SO transition to increase approximately 45% to a value that is 8 times larger than the gas phase value. We show that the magnitude of the increase is strongly correlated to the fraction of hcp crystal domains within the solid. Theoretical calculations presented in Paper II show that these intensity differences are caused by the different symmetries of single substitution sites for these two crystal structures. For fully annealed Br-atom doped pH2 solids, where the crystal structure is nearly pure hcp, the Br-atom SO transition sharpens considerably and shows evidence for resolved hyperfine structure.

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“…The SiF 4 monomers can probably migrate in solid pH 2 at the annealing temperature and the migration generates the dimers. Migration and clustering of dopants in annealed solid pH 2 were reported previously [26,27]. In the dense sample, these peaks were more distinct and increased after annealing for a few hours.…”

Section: Dimersmentioning

confidence: 67%