Radical Reactions in the Radiolysis of Cyclopentane

Wojnárovits, László; LaVerne, Jay A.

doi:10.1021/j100010a030

Cited by 9 publications

(18 citation statements)

References 7 publications

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“…The rate coefficients for the radical−radical reactions and radical−iodine scavenging reactions were as previously measured . Experimental values for cycloalkyl radical disproportionation/combination ratios were also used. ,, No experimental values for the rate coefficients for H atom−H atom combination or for H atom scavenging by iodine are available in hydrocarbon liquids. Since these reactions are nearly diffusion limited, the appropriate value in each of the cycloalkanes was obtained by a viscosity scaling of the rate coefficients in water .…”

Section: Methodsmentioning

confidence: 99%

“…The initial radiation chemical yields ( G values, in units of molecules/100 eV energy absorbed) for the excited singlet state and the excess molecular hydrogen were taken to be the same as found in the scavenging experiments . Because that study did not take into account H atom reactions with cycloalkyl radicals, the yields of the excited triplet states were increased slightly to give the same total dehydrogenation product yields as measured experimentally.…”

Section: Methodsmentioning

confidence: 99%

“…Because that study did not take into account H atom reactions with cycloalkyl radicals, the yields of the excited triplet states were increased slightly to give the same total dehydrogenation product yields as measured experimentally. The branching ratios for the decomposition of each excited state were taken to be the same as found previously . For each cycloalkane, the overall rate of decay of the singlet state was assumed to be the inverse of the measured or estimated lifetime .…”

Section: Methodsmentioning

confidence: 99%

“…Cyclic hydrocarbons are in many respects the simplest liquid hydrocarbons to study because they have only a few decomposition modes leading to the formation of the H atom, the cycloalkyl radical, H 2 molecule, and the cycloalkene. , With only a few reactive species, the variety of products is reduced, and radical scavenging techniques can readily give information on the temporal evolution of the spur. Recently, a number of studies were combined to give a rather complete mechanism for the radiolytic decomposition of cyclopentane, cyclohexane, and cyclooctane . That work offered estimates of the yields of transients produced, but many of complexities of the nonhomogeneous kinetics were not examined.…”

Section: Introductionmentioning

confidence: 99%

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Diffusion−Kinetic Modeling of the γ-Radiolysis of Liquid Cycloalkanes

1997

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A deterministic diffusion−kinetic model has been successfully applied to the radiation chemistry occurring in a typical spur produced in the γ-radiolysis of liquid cyclopentane, cyclohexane, and cyclooctane. The predictions of the yields of the cycloalkenes, bicycloalkyls, and the cycloalkyl iodides in solutions of iodine are in excellent agreement with experimental data. The major adjustable parameters in the model are the characteristic radii of the initial Gaussian spatial distributions of the reactive species. Values for these radii were found to be 0.5, 1.1, and 0.55 nm in cyclopentane, cyclohexane, and cyclooctane, respectively. The results suggest that the spurs of cyclopentane and cyclooctane are very small, ca. one molecular diameter, with resulting large local concentrations of reactants. With cyclohexane, the spur size is twice as large and the initial local concentrations are an order of magnitude smaller. The experimentally observed temporal invariance of the cyclohexyl radical can be explained by competing effects in the spur evolution. Details and implications of the spur model are discussed.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Diffusion−Kinetic Modeling of the γ-Radiolysis of Liquid Cycloalkanes

1997

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“…For example, the yields of molecular hydrogen and cycloalkenes have been determined in the decomposition of the singlet excited states induced in irradiated cycloalkanes. 3 It is further well established that the yields of final products are usually dependent on the type of irradiating particle. 4 Energy deposited by the passage of ionizing radiation is nonhomogeneously distributed in the medium.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence in the Heavy Ion Radiolysis of Benzene

LaVerne

1996

J. Phys. Chem.

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Fluorescence emission has been measured in the radiolysis of neat liquid benzene with 1-15 MeV protons, 5-20 MeV helium ions, 5-30 MeV lithium ions, and 10-30 MeV carbon ions using single photon counting techniques. Companion studies were performed with 90 Sr-90 Y -particles with an average energy of about 1.66 MeV. Within 30-50 ns following the passage of the heavy particles the fluorescence intensity decreases rapidly and then levels off to a much slower decay rate which is very nearly the same for -particles and high-energy protons and helium ions. The lifetimes of both the fast and slow components of the fluorescence decrease with increasing linear energy transfer (LET), and the magnitude of the fast component increases with respect to the slower one. Quenching of the fluorescence by radicals or other transient species produced in the particle track are thought to be responsible for the observations. At low LET the relative yield of the fluorescence decreases with increasing LET, presumably due to the quenching. However, at higher LET the fluorescence yield increases with increasing LET. Self-annihilation reactions of the triplet states to give singlet states may be the source of these observations. These experiments are the first in which the temporal variation of fluorescence emission has been determined in a neat hydrocarbon liquid irradiated with heavy ions.

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