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Shevtsov, V. A.; Malmi, Pekka; Ylinen, E.E.; Punkkinen, M.

doi:10.1023/a:1021802220741

Cited by 9 publications

(9 citation statements)

References 3 publications

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“…Recently, our group 2 found that the rate constant for the tunneling reaction remarkably increases with the increase in temperature between 5 and 6.5 K, whereas that calculated based on a gas-phase model [3][4][5] has not predicted such an increase. The apparent activation energy for the reaction ͑90 K͒ obtained by fitting the rate constant between 5 and 6.5 K to Arrhenius' equation is very close to that for vacancy formation and migration in solid H 2 (ϳ100 K͒ deduced from temperature dependence of diffusion rate constants of ortho-H 2 ͑o-H 2 ), 6 HD, 7,8 H 2 Ϫ , 9 and charged species. 10 Therefore, it is expected that the tunneling reaction is affected by the vacancy in solid HD.…”

Section: Introductionsupporting

confidence: 61%

Trapping sites of hydrogen atoms in solid HD and D2: An electron spin echo study

Kumada

Noda

Kumagai

et al. 1999

The Journal of Chemical Physics

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Absence of recombination of neighboring H atoms in highly purified solid parahydrogen: Electron spin resonance, electron-nuclear double resonance, and electron spin echo studies Trapping sites of H and D atoms in solid HD and D 2 have been determined using electron spin echo ͑ESE͒ spectroscopy. It was found that all the H and D atoms are trapped in substitutional sites and that the H atoms push back surrounding HD(D 2 ) molecules to produce local lattice distortion around the atoms, whereas the D atoms do not. It is expected that the local lattice distortion is produced by zero-point motion of the H atoms whose amplitude is larger than that of host HD(D 2 ) molecules and that the isotope effect is due to difference in the amplitude between the H and D atoms. The lattice distortion around the H atoms may induce the increase in rate constant for the tunneling reaction DϩDH→D 2 ϩH with the increase in temperature in solid HD reported in Chem.

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Section: Introductionsupporting

confidence: 61%

Trapping sites of hydrogen atoms in solid HD and D2: An electron spin echo study

Kumada

Noda

Kumagai

et al. 1999

The Journal of Chemical Physics

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“…7 Ortho-para conversion in solid hydrogen catalyzed by O 2 paramagnetic impurities (less than 0.1%) has been extensively studied at low temperatures using nuclear magnetic resonance spectroscopy. [8][9][10] The magnetic dipole interaction involving H 2 and O 2 species is decreasing very rapidly with their relative distance R (as 1/R 6 ). Consequently, the conversion induced by local catalysis centred around O 2 species has been used to investigate molecular diffusion in solids.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, the conversion induced by local catalysis centred around O 2 species has been used to investigate molecular diffusion in solids. [8][9][10][11][12][13][14] The conversion of o-H 2 to p-H 2 has been observed by infrared spectroscopy in microporous D 2 O ice formed at 12 K and saturated with H 2 . The time evolution of the complex spectra observed reveals a relaxation with a half time of 45 min.…”

Section: Introductionmentioning

confidence: 99%

Nuclear spin conversion of molecular hydrogen on amorphous solid water in the presence of O₂traces

Chehrouri

Fillion

Chaabouni

et al. 2011

Phys. Chem. Chem. Phys.

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Nuclear spin conversion (NSC) of ortho- to para-H(2) and para- to ortho-D(2) has been investigated on an amorphous solid water (ASW) surface at 10 K, in the presence of co-adsorbed O(2). The dynamics of the nuclear spin conversion could be revealed by combination of resonance enhanced multiphoton ionization spectroscopy (REMPI) with temperature programmed desorption (TPD) experiments. The conversion rates are consistent with a diffusion of molecular hydrogen inducing a nuclear spin conversion enhanced in the vicinity of molecular oxygen. The conversion times were found to increase with decreasing O(2) and H(2) coverage. Finally, on oxygen free ASW surface, the extremely long conversion characteristic times measured showed that such surface is not an efficient catalyst for NSC, in contradiction with hypothesis commonly made for interstellar medium.

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“…Table The appreciable extent controlled by rather strong anisotropic interactions, which tend to compress these solids. In addition, the paramagnetic impurities of oxygen can essentially affect the conversion process in the normal hydrogen crystals [20][21][22]. Some of preliminary results of hydrogen doped with Ar, Kr, and N 2 have been reported at the 3rd Cryocrystals Conference [23].…”

Section: Resultsmentioning

confidence: 99%

Properties of solid hydrogen doped by heavy atomic and molecular impurities

Galtsov

Prokhvatilov

Shcherbakov

et al. 2003

Low Temperature Physics

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Using powder x-ray diffraction we studied the structural characteristics of normal and para hydrogen crystals doped with Ar, Kr, N 2 , and O 2 impurities over the range from 5 K to the melting point of the hydrogen matrix. It has been established that in spite of very low solubility of the dopants in solid hydrogen, these impurities appreciably affect the structural characteristics. In particular, only nitrogen impurities do not change the molar volume of the matrix, the other three make the matrix expand. The Ar and Kr impurities also change the c/a ratio of the hcp matrix. The fact that both Ar and O 2 have smaller molar volumes than hydrogen may be treated as evidence that these impurities form van der Waals complexes with the hydrogen lattice environment.PACS: 67.80.Mg, 67.90.+z

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Cited by 9 publications

References 3 publications

Trapping sites of hydrogen atoms in solid HD and D2: An electron spin echo study

Trapping sites of hydrogen atoms in solid HD and D2: An electron spin echo study

Nuclear spin conversion of molecular hydrogen on amorphous solid water in the presence of O₂traces

Properties of solid hydrogen doped by heavy atomic and molecular impurities

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Untitled

Cited by 9 publications

References 3 publications

Trapping sites of hydrogen atoms in solid HD and D2: An electron spin echo study

Trapping sites of hydrogen atoms in solid HD and D2: An electron spin echo study

Nuclear spin conversion of molecular hydrogen on amorphous solid water in the presence of O2traces

Properties of solid hydrogen doped by heavy atomic and molecular impurities

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Nuclear spin conversion of molecular hydrogen on amorphous solid water in the presence of O₂traces