Exchange reactions between heavy hydrogen and hydrogen adsorbed in solids

Farkas, A.; Farkas, L.

doi:10.1039/tf9353100821

Cited by 15 publications

(16 citation statements)

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“…The first series of experiments were performed by Farkas and Farkas in 1935 soon after deuterium became available in quantities sufficient for kinetic studies. 1 From the analysis of reaction orders and activation energies, the authors reached the conclusion that the exchange proceeds via a three-center atomic displacement mechanism H + D2 -D + H 2 , preceded by a fast dissociative preequilibrium of the hydrogen (and deuterium) molecule.…”

Section: Introductionmentioning

confidence: 99%

The reaction H2+D2⇄2HD. A long history of erroneous interpretation of shock tube results

Lifshitz

Bidani

Carroll

1983

The Journal of Chemical Physics

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Rate constants for the reaction, H+D2→HD+D, over the temperature range, 724-2061 K, by the flash photolysis shock tube technique An ultraclean 2 in. Ld. single pulse shock tube coupled to an atomic resonance absorption system was constructed in order to determine hydrogen atom concentration by Lyman-a absorption. The tube was baked to 300·C and pumped down to _10-7 Torr. Ultrapure argon could be shock heated to -2500 K with no spurious H atom absorption. The system was constructed in order to study the kinetics of chemical reactions which are strongly catalyzed by H atoms, under the conditions where no such atoms are present. Specifically, the role of H atoms in the H2 + D2---+2HD exchange reaction was studied. Mixtures of hydrogen and deuterium diluted in argon were shock heated to 1375-1760 K; samples were then taken from the tube and analyzed mass spectrometrically for the ratio [HD]/[D2J. 1400 K was the highest temperature at which no spurious H atom absorption was observed in a shocked mixture of 1% H2-1 % D 2 . At 1400 K, under the conditions of no absorption, no, or s; I %HD conversion was obtained. At higher temperatures Lyman-a absorption was detected and more HD conversion was observed. A comparison between these results and results obtained previously in conventional systems suggests that the high HD conversion observed in the past was caused by hydrogen atoms generated from impurities. The existence of a molecular mechanism in the H2-D2 exchange reaction is highly doubtful.2742

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Section: Introductionmentioning

confidence: 99%

The reaction H2+D2⇄2HD. A long history of erroneous interpretation of shock tube results

Lifshitz

Bidani

Carroll

1983

The Journal of Chemical Physics

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“…The reaction proceeds by an ionic mechanism (Thompson and Schaeffer 1958), and the rate limiting step is the reaction of one hydrogen molecule with an ion of the other kind of hydrogen. This yields a 'first-order' equation in terms of the hydrogen molecules (Farkas and Farkas 1935). We therefore analyse our data on an exponential basis.…”

Section: Resultsmentioning

confidence: 99%

Broadband x-ray optical elements based on aperiodic multilayer structures

Kolachevsky¹,

Pirozhkov²,

Рагозин³

2000

Quantum Electron.

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Collision-induced infrared spectroscopy has been used to measure the initial rate of the chemical exchange of equimolar D2 and T2 in liquid and solid forms from 9 to 23 K over 23 to 45 h. If first-order kinetics are assumed, the time constant is 100-140 h for thermal equilibrium and 16C-180 h for a hot-atom equilibrium. The latter is favoured, but cannot be confirmed. Approximately three DT molecules are formed per ion pair (using the gas-phase value of 36.6 eV/ion pair). A likely mechanism is reaction of the T2+ to the TT ion, followed by exchange. The slowness of the exchange suggests that molecular DT can be isolated and handled for fusion applications.

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“…The ratio of the two isomers is determined by the Boltzmann thermal equilibrium for the given rotational state J , Figure 8. [200] For a more detailed discussion of the physics and applications of parahydrogen beyond the scope of this mini-review, we refer the interested reader to the 1935 book by Farkas on hydrogen [200] or various excellent discussions. [201] …”

Section: Parahydrogenmentioning

confidence: 99%

NMR Hyperpolarization Techniques of Gases

Barskiy

Coffey

Nikolaou

et al. 2016

Chemistry A European J

157

117

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Nuclear spin polarization can be significantly increased through the process of hyperpolarization, leading to an increase in the sensitivity of nuclear magnetic resonance (NMR) experiments by 4–8 orders of magnitude. Hyperpolarized gases, unlike liquids and solids, can be more readily separated and purified from the compounds used to mediate the hyperpolarization processes. These pure hyperpolarized gases enabled many novel MRI applications including the visualization of void spaces, imaging of lung function, and remote detection. Additionally, hyperpolarized gases can be dissolved in liquids and can be used as sensitive molecular probes and reporters. This mini-review covers the fundamentals of the preparation of hyperpolarized gases and focuses on selected applications of interest to biomedicine and materials science.

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Exchange reactions between heavy hydrogen and hydrogen adsorbed in solids

Cited by 15 publications

References 0 publications

The reaction H2+D2⇄2HD. A long history of erroneous interpretation of shock tube results

The reaction H2+D2⇄2HD. A long history of erroneous interpretation of shock tube results

Broadband x-ray optical elements based on aperiodic multilayer structures

NMR Hyperpolarization Techniques of Gases

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