Reactions of thermal hydrogen atoms at cryogenic temperature below 77 K as studied by ESR. Competitive hydrogen abstraction from ethane and hydrogen iodide in rare-gas matrixes

Muto, Hachizo; Nunome, Keichi; Iwasaki, Machio

doi:10.1021/j100462a018

Cited by 15 publications

(8 citation statements)

References 10 publications

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“…Early indications of long-range mobility of H atoms are derived from UV photolysis of HI in solid Xe codoped with C 2 H 6 with ESR analysis of reaction products. , The experiments demonstrated a competition between abstraction reactions of the hot H atoms with HI and ethane to form H 2 , instead of addition to the radicals. These observations are quite similar to those of F atoms 382 and would imply long-range migration of H atoms.…”

Section: H Atomsmentioning

confidence: 99%

“…These observations are quite similar to those of F atoms 382 and would imply long-range migration of H atoms. The unusual abstraction reaction with ethane, along with a very large isotope effect, is ascribed to reaction via tunneling. , …”

Section: H Atomsmentioning

confidence: 99%

“…The unusual abstraction reaction with ethane, along with a very large isotope effect, is ascribed to reaction via tunneling. 385,386 In thermal mobility studies, H and D atoms were produced by X-ray and VUV excitation from a large variety of hydrocarbons and triatomic and diatomic parent molecules in Xe, Kr, and Ar matrixes. [387][388][389] The atoms are stable for weeks at low temperatures but bleach at elevated temperatures through thermally activated diffusion.…”

Section: H Atomsmentioning

confidence: 99%

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Molecular Photodynamics in Rare Gas Solids

1999

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Section: H Atomsmentioning

confidence: 99%

Section: H Atomsmentioning

confidence: 99%

Section: H Atomsmentioning

confidence: 99%

See 1 more Smart Citation

Molecular Photodynamics in Rare Gas Solids

1999

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“…A number of groups have used hydrogen halides as precursors in the investigations of the properties and reactions of these atoms. [1][2][3][4][5][6][7][8][9][10][11] One of the most important facts has been the mobilization and subsequent disappearance of hydrogen atoms at 30-40 K. 2,3,6,7,9,10 UV excitation of rare-gas matrices doped with halogen atoms leads to charge-separation and permanent trapping of positive and negative charges as shown by Fajardo and Apkarian. [12][13][14] As a consequence of charge separation and trapping, several molecular ions such as (Xe 2 H) ϩ , (Kr 2 H) ϩ , (Ar 2 H) ϩ , (I 2 H) Ϫ , (Br 2 H) Ϫ , and (Cl 2 H) Ϫ , have been observed.…”

Section: Introductionmentioning

confidence: 99%

The mechanism of formation and infrared-induced decomposition of HXeI in solid Xe

Pettersson

Nieminen

Khriachtchev

et al. 1997

The Journal of Chemical Physics

118

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Ultraviolet ͑UV͒ irradiation of HI-doped xenon matrix dissociates the precursor and leads to the formation and trapping of neutral atoms. After UV photolysis, annealing of the matrix mobilizes the hydrogen atoms at about 38 K. The mobilized hydrogen atoms react with I/Xe centers forming HXeI molecules in a diffusion controlled reaction. The formed molecules can be photolyzed with infrared ͑IR͒ irradiation at 2950-3800 cm Ϫ1 and quantitatively regenerated thermally. The formation of HXeI from neutral atoms is proved by the quantitative correlation between neutral iodine atoms and HXeI molecules in selective IR photodissociation and thermal regeneration experiments. Kinetic measurements show that the formation of HXeI from atoms is prevented by a potential barrier, which is estimated to be 700 cm Ϫ1 in magnitude. The potential barrier is proposed to originate from the avoided crossing between neutral HϩXeϩI and ionic ͑HXe͒ ϩ ϩI Ϫ singlet surfaces. The dissociation energy D 0 of HXeI with respect to the top of the potential barrier is estimated to be 2950 cm Ϫ1 and D e about 4070 cm Ϫ1 in solid Xe. The weak IR photodissociation profile of HXeI around 3000 cm Ϫ1 is measured by irradiating the sample with tunable IR source and monitoring the changes in the fundamental region. The formation mechanism from neutral atoms is believed to be valid for other similar rare-gas compounds.

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“…Recent results on the tunneling reactions have been reviewed . Tunneling reactions of H atoms with hydrogen molecules have been studied in detail in solid hydrogen at very low temperature. , A tunneling reaction of H atoms with ethane was studied in a rare-gas matrix at 50 K …”

Section: Introductionmentioning

confidence: 99%

Temperature Effect on Selective Tunneling Abstraction Reaction by H Atoms in Neopentane−Alkane Mixtures at 4−100 K

et al. 1998

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When H atoms are produced by the photolysis of HI or the radiolysis of neo-C5H12 in the neo-C5H12−i-C4H10(2 mol %) mixtures above 40 K, the H atoms react selectively with the solute i-C4H10. The selective reaction is suppressed below 30 K. The reactions have been studied by electron spin resonance and electron spin echo measurements at 4−100 K. The drastic temperature effect on the reaction by H atoms suggests that the H atoms concerned are not hot atoms, but thermal atoms. The thermal H atoms react with the solute alkane by quantum tunneling at low temperature. Temperature effects on the ESR spectra and the spin−lattice relaxation times of the solvent neo-C5H11 radicals and the solute t-C4H9 radicals indicate that local motions of the solute i-C4H10 molecules take place above 40 K, while motions of the solvent neo-C5H12 molecules are severely restricted even at 100 K. It is concluded that the local motions of the solute i-C4H10 assist the tunneling abstraction reaction by H atoms, resulting in the selective reaction with the solute above 40 K.

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Reactions of thermal hydrogen atoms at cryogenic temperature below 77 K as studied by ESR. Competitive hydrogen abstraction from ethane and hydrogen iodide in rare-gas matrixes

Cited by 15 publications

References 10 publications

Molecular Photodynamics in Rare Gas Solids

Molecular Photodynamics in Rare Gas Solids

The mechanism of formation and infrared-induced decomposition of HXeI in solid Xe

Temperature Effect on Selective Tunneling Abstraction Reaction by H Atoms in Neopentane−Alkane Mixtures at 4−100 K

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