Radiolytic production of trapped hydrogen atoms from organic compounds in Xe, Kr, and Ar at 10 K
Trapped hydrogen atoms (H/sub t/ or D/sub t/) are shown to be formed by the radiolysis at 10 K of 0.5 mol % of CH/sub 4/, C/sub 2/H/sub 6/, 3-methylpentane-h/sub 14/ (3MP), 3-methylpentane-d/sub 14/ (3MP-d/sub 14/), benzene, C/sub 2/H/sub 5/OH, or i-C/sub 4/H/sub 10/ in Xe, of 3MP-d/sub 14/ in Kr, and of C/sub 2/H/sub 6/ or 3MP-d/sub 14/ in Ar. This is consistent with the conclusion that the reason trapped atoms are not observed following similar radiolyses of neat organic compounds is because they are lost by prompt abstraction from C-H (or C-D) bonds. If no H/sub t/ or D/sub t/ were produced from the organic compounds in the inert gas matrices it would have been necessary to conclude that radical formation during radiolysis of neat organic solids occurs by proton transfer. The magnitudes of the trapped atom yields in the inert gas matrices require a contribution to bond rupture by transfer of energy or charge from the inert gas molecules to the organic species over several molecular diameters. The evidence indicates that, at least in the case of CH/sub 4/ in Xe, the transfer mechanism involves photon emission by excited matrix molecules and absorption by the organic solute molecules. The thresholds for the onset of decay of H/sub t/ occur at about 20 K in Ar, 30 K in Kr, and 40 K in Xe. In part at least, the decays follow second-order kinetics. The trapped radicals in Xe require a temperature of > 100 K for rapid decay. At doses > 1 x 10/sup 20/ eV g/sup -1/ the G(H/sub t/) in Xe-3MP decreases, and a steady-state plateau concentration of -- 5 x 10/sup -3/ M appears to be reached at -- 6 x 10/sup 20/ eV g/sup -1/. Possible mechanisms of the C-H (C-D) bond rupture are discussed. Equipment designed for prompt ESR examination of samples x irradiated at greater than or equal to 8 K and the nature of corrections for photoelectric absorpton of the x rays are described.
- Research Organization:
- Univ. of Wisconsin, Madison
- DOE Contract Number:
- EY-76-S-02-1715-A003
- OSTI ID:
- 6934728
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 85:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BENZENE
RADIOLYSIS
BUTANE
DEUTERIUM
TRAPPING
ETHANE
HYDROGEN
METHANE
ARGON
ATOMS
ELECTRON SPIN RESONANCE
KRYPTON
ULTRALOW TEMPERATURE
X RADIATION
XENON
ALKANES
AROMATICS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ELEMENTS
FLUIDS
GASES
HYDROCARBONS
HYDROGEN ISOTOPES
IONIZING RADIATIONS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RARE GASES
RESONANCE
STABLE ISOTOPES
400600* - Radiation Chemistry