Rotation of Methyl Radicals in Molecular Solids

Kiljunen, Toni; Popov, Evgeny; Kunttu, Henrik; Eloranta, Jussi

doi:10.1021/jp909316b

Cited by 21 publications

(71 citation statements)

References 22 publications

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“…The T-dependences of linewidths also demonstrate a more complicated nonmonotonic character as compared with found in the ESR spectra [12] but are similar in many respects to the CH 3 behavior in the CO matrices [13]. Two types of motion considered in our study evidently affect the radical motion.…”

Section: Resultssupporting

confidence: 73%

Hopping Precession of Molecules in Crystalline Carbon Dioxide Films

Krainyukova

Kuchta

2016

J Low Temp Phys

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We report a low-temperature transmission high-energy electron diffraction study of solid carbon dioxide films in the temperature range 15-87 K. The precise analysis of the experimental diffraction intensities shows that molecular axes noticeably deviate from the cubic space diagonals of the Pa3 structure. The molecular tips tend to be oriented toward the empty spaces between two molecules in the nearest basal planes. Nevertheless, the crystal structure is still identified as Pa3 but with 24 equivalent positions for oxygen atoms instead of 8 positions as it was thought before. We have shown that the relevant maximal angle deviations in the selected directions could be as big as ∼30 • at the lowest temperatures and they decrease at higher temperature. This results in hopping precession of molecules instead of simple librations.

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Section: Resultssupporting

confidence: 73%

Hopping Precession of Molecules in Crystalline Carbon Dioxide Films

Krainyukova

Kuchta

2016

J Low Temp Phys

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“…Comparing an experimental matrix shift, linewidth and superhyperfine splitting with the corresponding calculated parameters, one can either determine the trapping site of the atom or limit the number of possible sites. Kiljunen et al [24] presented ab initio and molecular-dynamics studies on rare gas hydrides. They calculated ground-state potential-energy curves and distance dependent isotropic hyperfine coupling constants for ground-state H-RG (=Ne, Ar, Kr, Xe).…”

Section: Hyperfine Structure Constantmentioning

confidence: 99%

EPR Study of H and D Atoms in Quench-Condensed Solid D $$_{2}$$ 2

Dmitriev

2015

J Low Temp Phys

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We present an experimental study of H and D atoms trapped in a solid D 2 matrix. The samples were prepared by quench condensing gaseous nD 2 with small (0.15 %) admixture of molecular nH 2 on a substrate at 1.3-4.2 K. An EPR observation revealed two types of H and D atoms: with narrow-and broad-line spectra. In order to elucidate the origin of the centers we performed an analysis that included comparing the matrix shifts of the hyperfine structure constants, considering the saturation and spin-relaxation times, estimation of the superhyperfine broadening, and evaluation of an effect which the tunneling isotope exchange reaction has on the H and D atoms relative EPR intensities. As a result, the broad-line H and D spectra were attributed to atoms at the substitutional positions in the regular D 2 lattice, while the narrow-line spectra were due to atoms trapped at the one-dimensional structure imperfections (like dislocations). These trapped atoms are capable of moving quickly along the defects with a diffusion coefficient D ≈ 4 × 10 −6 cm 2 /s. The results were compared to earlier observations which allowed us to build a suggestion about the nature of previously found atomic centers in D 2 not explained in the literature.

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“…Methyl radical plays a relevant role in many fields of research, as in biochemistry [1,2], in solid state and chemical physics [3][4][5][6][7][8][9][10] and in geology [11]. It is usually recognized in EPR spectra by its characteristic multiplet of four hyperfine components with relative intensities 1:3:3:1 (for T>40 K) and about 2.29 mT splitting between adjacent lines.…”

Section: Introductionmentioning

confidence: 99%

“…Methyl radicals were also observed and characterized in a variety of clathrate and zeolite materials [11,12], where they are generated by radiation induced dissociation of a fraction of the CH 4 molecules which naturally reside into the cages/channels of these materials. Finally, many efforts have been also devoted to characterize methyl radicals isolated in inert matrices at very low temperatures (T= 4 K), as in these special conditions they exhibit the typical features of a planar quantum rotor [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

“…Here we report a characterization and a comparative discussion of the properties of the hindered rotations motion observed at T = 77 K for CH 3 • molecules trapped in γ-ray irradiated high-purity a-SiO 2 and in the SiO 2 -clathrate Melanophlogite. This latter material is a naturally occurring SiO 2 -based clathrate structure which shares the same crystalline structure of type I gas hydrates [13].…”

Section: Introductionmentioning

confidence: 99%

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