Ortho-para conversion of hydrogen molecules physisorbed on surfaces

Ilisca, E.

doi:10.1016/0079-6816(92)90019-e

Cited by 91 publications

(97 citation statements)

References 150 publications

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“…We employ an online catalytic converter to transform ortho-H 2 into para-H 2 : before entering the cluster source the hydrogen gas passes through a small container cooled down to 15 K and filled with a catalyst (here Al 2 O 3 powder). 44 In this way nearly all the ortho-H 2 is converted into para-H 2 (at 20 K and thermal equilibrium already 99.8% of the molecules are in the para state 45 ). The mean size of rare gas and para-hydrogen clusters depends on the expansion parameters and can be estimated with the help of scaling laws 46 and measured values of argon, 47,48 neon, 48 and para-hydrogen clusters.…”

Section: Methodsmentioning

confidence: 99%

Spectroscopy of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) attached to rare gas samples: Clusters vs. bulk matrices. I. Absorption spectroscopy

Dvořák

Müller

Knoblauch

et al. 2012

The Journal of Chemical Physics

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The interaction between 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) and rare gas or para-hydrogen samples is studied by means of laser-induced fluorescence excitation spectroscopy. The comparison between spectra of PTCDA embedded in a neon matrix and spectra attached to large neon clusters shows that these large organic molecules reside on the surface of the clusters when doped by the pick-up technique. PTCDA molecules can adopt different conformations when attached to argon, neon, and para-hydrogen clusters which implies that the surface of such clusters has a well-defined structure without liquid or fluxional properties. Moreover, a precise analysis of the doping process of these clusters reveals that the mobility of large molecules on the cluster surface is quenched, preventing agglomeration and complex formation.

show abstract

Section: Methodsmentioning

confidence: 99%

Spectroscopy of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) attached to rare gas samples: Clusters vs. bulk matrices. I. Absorption spectroscopy

Dvořák

Müller

Knoblauch

et al. 2012

The Journal of Chemical Physics

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“…Expansions of the basic idea have included a variety of other interactions, many of which pertain primarily to magnetic surfaces [43,44].…”

Section: (B) Paramagnetic Catalysis Of Intersystem Crossing In Spin Amentioning

confidence: 99%

Nuclear spin isomers of guest molecules in H ₂ @C ₆₀ , H ₂ O@C ₆₀ and other endofullerenes

Chen

Frunzi

et al. 2013

Phil. Trans. R. Soc. A.

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Spectroscopic studies of recently synthesized endofullerenes, in which H 2 , H 2 O and other atoms and small molecules are trapped in cages of carbon atoms, have shown that although the trapped molecules interact relatively weakly with the internal environment they are nevertheless susceptible to appropriately applied external perturbations. These properties have been exploited to isolate and study samples of H 2 in C 60 and other fullerenes that are highly enriched in the para spin isomer. Several strategies for spin-isomer enrichment, potential extensions to other endofullerenes and possible applications of these materials are discussed.

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“…The para-state-enriched hydrogen gas is produced using "para-hydrogen generator" that works on principle of conversion of o H 2 to p H 2 on thermally dehydrated HFeO 2 surface cooled in cryostat to temperatures 10-18 K [30]. In this experiment normal hydrogen ( n H 2 ) is liquefied in the catalyst container and the saturated vapor of converted gas ( e H 2 ) is collected through an outlet tube.…”

Section: Methodsmentioning

confidence: 99%

State selective study of H₃⁺recombination in Cryo-FALP and SA-CRDS experiments at 77 K

Glosı́k

Hejduk

Dohnal

et al. 2015

EPJ Web of Conferences

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Abstract. Rate coefficients for nuclear spin state-specific recombination of H + 3 ions with thermal electrons were measured using FALP and SA techniques at temperatures 77-300 K. For this purpose H 2 gas with both thermal and enriched population of the para nuclear spin configuration was used. Measurements have shown that at 77 K para-H + 3 exhibits five times higher binary recombination rate coefficient than ortho-H + 3 : (1.5 ± 0.4) × 10 −7 vs. (3 ± 2) × 10 −8 cm 3 s −1 .

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Ortho-para conversion of hydrogen molecules physisorbed on surfaces

Cited by 91 publications

References 150 publications

Spectroscopy of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) attached to rare gas samples: Clusters vs. bulk matrices. I. Absorption spectroscopy

Spectroscopy of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) attached to rare gas samples: Clusters vs. bulk matrices. I. Absorption spectroscopy

Nuclear spin isomers of guest molecules in H ₂ @C ₆₀ , H ₂ O@C ₆₀ and other endofullerenes

State selective study of H₃⁺recombination in Cryo-FALP and SA-CRDS experiments at 77 K

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Ortho-para conversion of hydrogen molecules physisorbed on surfaces

Cited by 91 publications

References 150 publications

Spectroscopy of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) attached to rare gas samples: Clusters vs. bulk matrices. I. Absorption spectroscopy

Spectroscopy of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) attached to rare gas samples: Clusters vs. bulk matrices. I. Absorption spectroscopy

Nuclear spin isomers of guest molecules in H 2 @C 60 , H 2 O@C 60 and other endofullerenes

State selective study of H3+recombination in Cryo-FALP and SA-CRDS experiments at 77 K

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Nuclear spin isomers of guest molecules in H ₂ @C ₆₀ , H ₂ O@C ₆₀ and other endofullerenes

State selective study of H₃⁺recombination in Cryo-FALP and SA-CRDS experiments at 77 K