A simple model for hydrogen atom reactions in neopentane-cyclohexane mixtures irradiated at 4.2 K

Iwasaki, Machio; Toriyama, Kazumi

doi:10.1021/j100475a008

Cited by 17 publications

(16 citation statements)

References 3 publications

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“…It should be mentioned, however, that Iwasaki, Toriyama and co-workers [44][45][46] ascribed the selective formation of protiated radicals in mixed crystals to reactions of thermal D-atoms rather than to exciton migration. The observed suppression of energy transfer at 4 K was considered to be the main evidence against the exciton mechanism (compare with Section 2.3.1).…”

Section: Events Leading To Radical Formationmentioning

confidence: 99%

“…and R2 H + I~I ~ 1~2 +H2 (2) were considered by Iwasaki and co-workers [44][45][46]48] to be the main mechanism for radical pair production (see Section 2.3.1) and for radical site migration (see Section 2.5), as well as for the preferential formation of protiated radicals in mixed crystals, mentioned above. The fact that no trapped H-atoms were detected in alkanes at 4.2 K [49] was attributed to their rapid tunnel abstraction reaction with surrounding molecules.…”

Section: R~h-~ R~ + Fl (1)mentioning

confidence: 99%

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Radiation effects in polyethylene and n-alkanes

Ungar

1981

J Mater Sci

138

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The effect of high-energy radiation on n-alkanes and polyethylene (PE) are reviewed. The article includes a description of (a) primary radiation events, formation, spatial distribution and decay of free radicals and radical migration mechanisms, (b) formation of cross-lin ks and other sta ble products, (c) the effects of crystal linity, crystalline modifications and morphology on radiation cross-linking, and (d) radiation-induced changes in the crystal lattice and the destruction of crystallinity at high irradiation doses.An attempt is made to bring together conflicting views on various unsolved problems of the radiation physics and chemistry of these important and much studied substances. Long-chain paraffins are given considerable attention since their radiation behaviour often provides a link between that of PE and its short-chain analogues.

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Section: Events Leading To Radical Formationmentioning

confidence: 99%

Section: R~h-~ R~ + Fl (1)mentioning

confidence: 99%

Radiation effects in polyethylene and n-alkanes

Ungar

1981

J Mater Sci

138

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“…A number of methods have been described to include nuclear quadrupole effects smaller than the nuclear Zeeman interaction (8, [11][12][13][14][15][16][17][18][19][20][21]. The general result is to add two or more additional parameters to be determined by the simulated fit to the experimental data which often makes it difficult to obtain a unique set of five or more parameters.…”

Section: Analysis Of Nuclear Modulationmentioning

confidence: 99%

Applications of Electron Spin Echo Modulation

Kevan¹

1998

Foundations of Modern EPR

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Electron spin echoes are a consequence of particular resonance microwave pulse sequences in pulsed electron spin resonance (ESR) experiments. The pulse sequences reorient the electron magnetic dipoles such that they dephase and then rephase to reform a macroscopic magnetic moment which is detected as a burst of microwave energy called an echo. Spin echoes were first discovered for nuclear spins in early nuclear magnetic resonance experiments by Hahn while a graduate student at the University of Illinois in 1950 (1). Nuclear spin echoes were initially demonstrated for protons in various liquids such as glycerin and water. Interestingly, this original paper on nuclear spin echoes also reports observations of modulation of the spin echo response reflecting nuclear spin -nuclear spin coupling. The nuclear modulation effect was first demonstrated for protons in liquid ethanol corresponding to interactions between different groups of nonequivalent protons which have different molecular environments in the molecule.The first electron spin echoes were observed by Blume at Columbia University in 1958 for solvated electrons in sodium-ammonia solutions (2). With electron spin echoes the analogous modulation effect occurs between interactions of the electron spins with surrounding nuclear spins in different local magnetic environments. Hence, this is related to an electron-nuclear dipolar hyperfine interaction which is averaged to zero by rapid molecular tumbling in liquids. Consequently, in the original electron spin echo experiments in liquid ammonia no nuclear modulation effects were seen. The first observation of nuclear modulation effects in electron spin echo signals was reported in 1961 by Mims, Nassau and McGee at Bell Laboratories (3a) who observed the electron spin echo of cerium(III) doped into calcium tungstate modulated by the 183 W nuclei in the solid single crystal and by Cowan and Kaplan at Lockheed Research Laboratories who observed 14 N modulation of cerium(III) in lanthanum magnesium nitrate (3b). Subsequently, Mims and coworkers described electron spin echo modulation in detail and developed it as a new and useful scientific technique.The basic theory of the nuclear modulation effect on electron spin echo intensities was first given by Rowan, Hahn and Mims (4) in 1965 who described how to calculate the expected nuclear modulation pattern from a given geometrical model. Their description referred to single crystal experiments for a particular 641 Foundations of Modern EPR Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 10/04/15. For personal use only.

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“…in irradiated methanol at 4 K were determined for the first time by Iwasaki and Toriyama in 1978 [22]. Furthermore, they investigated experimentally the reactions occurring by radiolysis of polycrystalline methanol [23] and concluded that the formation of C H 2 0 H is caused by a unimolecular process from CH30., i.e., according to reaction (14).…”

Section: Rimentioning

confidence: 99%

Theoretical study on solvation effects in chemical reactions: A vibrational coupling model

Tachikawa

Lunell

Törnkvist

et al. 1992

Int J of Quantum Chemistry

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A vibrational coupling model to treat the solvation effects in chemical reaction rate calculations is proposed and applied to the intramolecular hydrogen transfer reaction CH30. + C H L O H in the condensed phase. The effect of solvation is taken into account in two ways: (1) the solvent effect on the activation energy of the reaction is simulated by including 39 surrounding water molecules, represented by fractional charges at the assumed atomic positions, in the potential energy surface calculation; and (2) the vibrational couplings between the 10 nearest solvent molecules and the molecules constituting the reaction system are explicitly included in a vibrational frequency calculation. RRKM theory with Miller's tunneling correction included is employed to calculate the rate constants. The effect of solvation causes a significant change in the chemical reaction rate, mainly through a lowering of the activation energy. The vibrational coupling causes a slight increase of the rate constant in the tunneling region by perturbing the vibrational frequencies of the reactant and transition states, which appear in the rate-constant expression, but has little effect at higher temperatures.

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A simple model for hydrogen atom reactions in neopentane-cyclohexane mixtures irradiated at 4.2 K

Cited by 17 publications

References 3 publications

Radiation effects in polyethylene and n-alkanes

Radiation effects in polyethylene and n-alkanes

Applications of Electron Spin Echo Modulation

Theoretical study on solvation effects in chemical reactions: A vibrational coupling model

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