Trapped hydrogen atoms, deuterium atoms, and methyl radicals in CH/sub 4/ and CD/sub 4/ at 5 to 50 K. Yields from photolysis of HX and from radiolysis; decay mechanisms; reactions with O/sub 2/ and CO

Journal Article · Thu May 14 04:00:00 EDT 1981 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j150610a009· OSTI ID:6372701

Bhattacharya, D; Wang, H Y; Willard, J E

This paper reports an investigation of the yields, decay properties, chemical reactions, and ESR saturation properties of trapped hydrogen atoms (H/sub t/ and D/sub t/) and methyl radicals (CH/sub 3/ and CD/sub 3/) formed by the radiolysis of CH/sub 4/ and CD/sub 4/ at 5 K and by the 254-nm photolysis of HI and DI and the 185-nm photolysis of HBr in CH/sub 4/ and CD/sub 4/ at 5 K. The quantum yields depend on the isotopic nature of the atoms and the matrix, and on the HX source. The observed products from the photolysis of HBr or HI in CD/sub 4/ are H/sub t/ and CD/sub 3/, formed by hot abstraction, and D/sub t/, formed in part by the H + CD/sub 4/ ..-->.. CD/sub 3/H + D displacement and in part by the photodecomposition of CD/sub 3/. The decay rates at higher temperatures are slower in CD/sub 4/ than in CH/sub 4/ and depend on the isotope and its photolytic source. The decay rates of H/sub t/ and D/sub t/ from HX are composite first order. The atoms remaining after approx. 50% have decayed are able to react with dissolved CO forming HCO, O/sub 2/ forming HO/sub 2/, and C/sub 2/H/sub 6/ forming C/sub 2/H/sub 5/. More than 90% of the H/sub t/ produced by X radiolysis of neat CH/sub 4/ decays by H + H ..-->.. H/sub 2/. Ca. 38% of the CH/sub 3/ produced when HI is photolyzed in CH/sub 4/ decays concurrent with H/sub t/ decay at <20 K. Rapid decay of the remaining CH/sub 3/ from both photolysis and radiolysis occurs only at >45 K, for which comparative rates are reported. The threshold powersfor ESR saturation of H/sub t/, D/sub t/, CH/sub 3/, and CD/sub 3/ range from <0.05 ..mu..W (the lowest power used) to >1 mW. Tests for the production of H/sub t/ and D/sub t/ by the photolysis of HI in several polycrystalline hydrocarbons have given negative results. Evaluation of absorbed X-ray dose rates by samples of different average atomic number is described.

• Research Organization: Univ. of Wisconsin, Madison
• OSTI ID: 6372701
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 85:10; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400500 -- Photochemistry
400600* -- Radiation Chemistry
ALKANES
ALKYL RADICALS
ATOMS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
DECAY
DECOMPOSITION
DEUTERIUM
DEUTERIUM COMPOUNDS
ELECTROMAGNETIC RADIATION
ELEMENTS
G VALUE
GAMMA RADIATION
HALOGEN COMPOUNDS
HYDRIODIC ACID
HYDROBROMIC ACID
HYDROCARBONS
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
INORGANIC ACIDS
IODINE COMPOUNDS
IONIZING RADIATIONS
ISOTOPES
LIGHT NUCLEI
METHANE
METHYL RADICALS
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADICALS
RADIOLYSIS
STABLE ISOTOPES
TRAPPING
VERY LOW TEMPERATURE