Ortho-para conversion in solid hydrogen, catalyzed by molecular oxygen impurities

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

doi:10.1007/bf00754095

Cited by 24 publications

(12 citation statements)

References 14 publications

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“…͑21͒ with k D using a quantum diffusion constant for the lithium impurity. While there have been numerous experimental and theoretical studies for diffusion of atomic and molecular impurities within the solid hydrogen, [45][46][47][48] no data are available for lithium impurity. Since lithium atom diffusion is likely correlated with vacancy diffusion, it can be expected to be of the same order as the H 2 self-diffusion rate, which is approximately 1ϫ10 Ϫ24 cm 2 s Ϫ1 at 4 K. Using ϭ15 Å and v r ϭ4 3 /3, the approximate quantum rates are then estimated to be k i ϭ3ϫ10 Ϫ17 cm 3 s Ϫ1 and k D ϭ2ϫ10 Ϫ30 cm 3 s Ϫ1 .…”

Section: Discussionmentioning

confidence: 98%

Lithium impurity recombination in solid para-hydrogen: A path integral quantum transition state theory study

Jang

Voth

1998

The Journal of Chemical Physics

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Molecular collective dynamics in solid para-hydrogen and ortho-deuterium: The Parrinello-Rahman-type path integral centroid molecular dynamics approach J. Chem. Phys. 119, 953 (2003); 10.1063/1.1578474Quantum molecular dynamics and spectral simulation of a boron impurity in solid para-hydrogenThe recombination of two lithium atoms trapped in one-vacancy defect sites of solid para-hydrogen at 4 K and zero external pressure is studied as a quantum activated process. The quantum activation free energy is calculated using path integral quantum transition state theory along with the method of path integral molecular dynamics simulation. The equilibrium volume of the system is determined by a constant pressure method that scales the sides of the rectangular simulation box. At a fixed equilibrium volume of the system, a constraint dynamics path integral simulation is then employed to determine the quantum path centroid free energy barrier along the reaction coordinate, which is taken to be the relative Li-Li separation. The two lithium atoms begin to recombine at a distance of approximately twice the lattice spacing, and the height of the barrier relative to the metastable well is 78Ϯ10 K. The rate of the intrinsic recombination step is estimated to be 1.3 ϫ10 3 s Ϫ1 at 4 K. It is found that the lithium nuclei exhibit significant tunneling behavior over their classical limit.

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Section: Discussionmentioning

confidence: 98%

Lithium impurity recombination in solid para-hydrogen: A path integral quantum transition state theory study

Jang

Voth

1998

The Journal of Chemical Physics

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“…Clearly the measured decay in X o is significantly greater than the predicted self-conversion rate indicating that the Cl-atoms catalyze the o/p conversion. The X o data are well fit by an expression developed for catalyzed conversion by O 2 molecules [30], namely…”

Section: Cl-atom Decay Profiles In Solid H 2 With X O ≈ 055 and 003mentioning

confidence: 99%

Infrared studies of ortho-para conversion at Cl-atom and H-atom impurity centers in cryogenic solid hydrogen

Kettwich

Anderson

2010

Low Temperature Physics

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We report infrared spectroscopic studies of H 2 ortho-para (o/p) conversion in solid hydrogen doped with Clatoms at 2 K while the Cl + H 2 (v = 1) → HCl + H infrared-induced chemical reaction is occurring. The Cl-atom doped hydrogen crystals are synthesized using 355 nm in situ photodissociation of Cl 2 precursor molecules. For hydrogen solids with high ortho-H 2 fractional concentrations (X o = 0.55), the o/p conversion kinetics is dominated by Cl-atom catalyzed conversion with a catalyzed conversion rate constant K cc = 1.16 (11)

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“…A second candidate for fitting the ortho signal is obtained by replacing the sine function in f gs with the first-order Bessel function J 1 (12,14),…”

Section: Resultsmentioning

confidence: 99%

Separation of the Ortho and Para NMR Signals in Solid Deuterium via DQ Filtering

Malmi

Punkkinen

Ylinen

et al. 2000

Journal of Magnetic Resonance

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Ortho-para conversion in solid hydrogen, catalyzed by molecular oxygen impurities

Cited by 24 publications

References 14 publications

Lithium impurity recombination in solid para-hydrogen: A path integral quantum transition state theory study

Lithium impurity recombination in solid para-hydrogen: A path integral quantum transition state theory study

Infrared studies of ortho-para conversion at Cl-atom and H-atom impurity centers in cryogenic solid hydrogen

Separation of the Ortho and Para NMR Signals in Solid Deuterium via DQ Filtering

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