Electron paramagnetic resonance spectrum of the methyl radical adsorbed on a silicagel surface

Pariiskii, G.B.; Zhidomirov, G. M.; Kazanskii, V. B.

doi:10.1007/bf00745534

Cited by 4 publications

(18 citation statements)

References 5 publications

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“…Model I suggests slightly hindered rotation occurring about the C 3 -symmetry axis while the rotation about the in-plain axes is restricted. The same bound geometry was considered by Pariiskii et al As a result, an axially symmetric EPR line shape was expected. The spectrum was, indeed, observed by Shiga and Lund .…”

Section: Discussionmentioning

confidence: 66%

“…While the quantum potential modifies the levels by adding energy to the system, probably without a significant change in the level separation, in the classical case it has to be considered as a hindrance of the rotation thus reducing the kinetic energy of the system. This is taken by certain workers as a reduction of the kinetic constant of the radical, which then leads to decreasing level separation and consequently to the classical limit of the system. , …”

Section: Spin-rotation Levels Of Methylmentioning

confidence: 99%

“…Pariiskii et al are inconsistent in their article by using both the terms “intensity” and “amplitude” for the same ratio of their experimental methyl quartet transitions. They write, namely, that the “intensity” distribution 1:8.5:13:2.5 does not satisfy the binomial law 1:3:3:1, while, in a different part, they refer to the same ratio as unusual “amplitude” ratio.…”

Section: Introductionmentioning

confidence: 99%

“…In Pariiskii et al 10 there are conflicting statements describing the broadening mechanism of the EPR spectrum of methyl radical adsorbed on the surface of silica gel. At first, they state that hindering the thermal motion of the radical leads to broad and anisotropic spectra and intensity of the central components below the magnitude corresponding to the binomial distribution, in spite of the fact that they observe the opposite relation of the central to the outer spectral components.…”

Section: ■ Introductionmentioning

confidence: 99%

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Anomalous EPR Intensity Distribution of the Methyl Radical Quartet Adsorbed on the Surface of Porous Materials. Comparison with Solid Gas Matrix Isolation

Benetis

Dmitriev

2013

J. Phys. Chem. A

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The two inner lines of the EPR quartet of methyl radicals trapped in cryogenic gas matrices are superpositions of the inner transitions of an A-proton-spin quartet and an E-proton-spin doublet. Their intensity relative to the outer lines provides information on the population of the methyl-rotation quantum states. The above intensity ratio for the CH3 in solids is a challenging problem of the quantum dynamics and statistical thermodynamics. The influence of the quantum-mechanical/inertial rotation on the intensity distribution of the hf components of methyl radical on the surface of porous materials, e.g., silica gel, is investigated by EPR line shape simulations and compared with spectra of the radical isolated in the bulk of solid gas samples. The experimental part of this study includes the first in literature EPR observation of methyl radical in the bulk of N2O solid and provides new essential information on CH3 in CO2 and Ar matrices, thus, covering both strongly hindered and almost free rotation of the radical. We verify the observation of nonrotating methyl radicals in a N2O matrix, discovered earlier in cold CO2, give a thorough account of their EPR characteristics, and explore their formation at the inner surface of porous materials. Combination of a classical spin-Hamiltonian with employment of quantum effects due to nuclear spin-rotation coupling and the radical symmetry were used to interpret the experimental spectral observations. The cause of experimentally found unexpected contribution of the excited degenerate E-doublets to the EPR spectrum down to 4.2 K and A/E transition amplitude ratios sometimes as high as ca. 1:8 at liquid-N2 temperature is sought. The validity of Bose-Einstein quantum (BEq-) statistics of the spin rotation states in addition to the classical Maxwell-Boltzmann (Boltzmann) statistics was also assessed against experimental population A/E-ratio data. The BEq-statistics were not previously applied to similar systems. Furthermore, detailed consideration of the laboratory/free space rotational degeneracy and the planarity of methyl radical was also included in this work.

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Section: Discussionmentioning

confidence: 66%

Section: Spin-rotation Levels Of Methylmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Anomalous EPR Intensity Distribution of the Methyl Radical Quartet Adsorbed on the Surface of Porous Materials. Comparison with Solid Gas Matrix Isolation

Benetis

Dmitriev

2013

J. Phys. Chem. A

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show abstract

“…In reality, it only approaches this nominal perfection at sufficiently high magnetic fields. At (say) X-band, the middle two lines are in fact in some systems actually split into two, due to higher-order hyperfine effects, as discussed in the literature [1,14,39,46,8,18,16] and below.…”

Section: Next We Examine Some Examples Of XL 3 Speciesmentioning

confidence: 96%