Electron spin resonance signals of abnormal alkyl radicals trapped on porous Vycor glass surfaces coated with metal oxides at 77.deg.K

1971 ◽  
Vol 75 (26) ◽  
pp. 4064-4065 ◽  
Author(s):  
Takashi Katsu ◽  
Michiyasu Yanagita ◽  
Yuzaburo Fujita
Keyword(s):  
Electron Spin Resonance ◽  
Metal Oxides ◽  
Electron Spin ◽  
Vycor Glass ◽  
Alkyl Radicals ◽  
Porous Vycor Glass ◽  
Spin Resonance ◽  
Glass Surfaces

Electron spin resonance studies of methyl radicals stabilized on porous VYCOR glass: various surface interactions, second-order splitting, and a linewidth temperature study

1970 ◽  
Vol 48 (17) ◽  
pp. 2685-2694 ◽  
Author(s):  
G. B. Garbutt ◽  
H. D. Gesser
Keyword(s):  
Electron Spin Resonance ◽  
High Temperature ◽  
Electron Spin ◽  
Second Order ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Potential Wells ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Spin Resonance

Electron spin resonance studies have been performed on methyl radicals stabilized on the surface of porous VYCOR glass. As previously reported, two very different methyl radicals, denoted Me and Me′, were seen. Results indicate that the radical Me′ is most probably weakly bound to the boroxane group (=B—O—B=) which is prominent on the surface of high temperature (700–900 °C) pretreated porous VYCOR glass. Four satellite lines about each Me line, denoted previously as radical X, were observed when the surface was pretreated at lower temperatures (400–500 °C). In an earlier publication radical X was attributed to the interaction between methyl radicals and the isotopic surface species 11B. In this study two additional satellite lines about each Me line are reported as well as a reassignment of the origin of all satellite lines. Four of the six satellite lines have been assigned to forbidden "spin–flip" transitions while the other two have been assigned to direct interaction between methyl radicals and the surface hydroxyl protons. Support for the irreversibility of high temperature dehydroxylation of porous VYCOR glass is also presented.A partial resolution of the second-order splitting of each of the central pair of lines was achieved for the normal methyl radical. The value of the second-order splitting was between 220 and 230 mG. The linewidths of the two central lines were measured at 77 °K. The samples were then allowed to warm up to various temperatures and then recooled to 77 °K. The linewidths were smaller after completing this cycle. Storage of the sample at 77 °K allowed the linewidths to return to their original values. These linewidths effects are explained by postulating the existence of two different types of potential wells on the surface.

An electron spin resonance study of ultraviolet photolyzed methanol adsorbed on porous high-silica glass

1969 ◽  
Vol 47 (8) ◽  
pp. 1375-1379 ◽  
Author(s):  
Michie Shimizu ◽  
H. D. Gesser ◽  
M. Fujimoto
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Silica Glass ◽  
Electron Spin Resonance Study ◽  
Surface Contaminants ◽  
Spin Resonance ◽  
High Silica ◽  
Glass Surfaces ◽  
Spin Resonance Study

The electron spin resonance (e.s.r.) spectra of •CH3, •CHO, H and/or D, and possibly •CH2OH or •CH2OD were found by the ultraviolet (u.v.) photolysis of methanol —OH or —OD on porous high-silica glass at 77 °K. These e.s.r. spectra resemble the results of the u.v. photolysis of X-irradiated methanol indicating that some perturbation and/or sensitization occurred in the molecules by the glass surface. The absence of e.s.r. spectra from the same systems on the acid-leached glass, on the totally fluorinated glass, or on the totally —OH covered glass suggests that (i) the co-existence of surface contaminants, such as Al and Zr and not B, and some of surface —OH could be responsible for producing these free radicals, and (ii) the methanols adsorbed on these glass surfaces are stabilized against u.v. photolysis.

Photolysis of surface methoxides on several metal oxides as studied by electron spin resonance

1973 ◽  
Vol 77 (24) ◽  
pp. 2837-2841 ◽  
Author(s):  
Shozo Kubota ◽  
Masamoto Iwaizumi ◽  
Taro Isobe
Keyword(s):  
Electron Spin Resonance ◽  
Metal Oxides ◽  
Electron Spin ◽  
Spin Resonance

Radiation damage in polyethylene as studied by electron spin resonance

1961 ◽  
Vol 262 (1309) ◽  
pp. 207-218 ◽  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Alkyl Radical ◽  
Room Temperature ◽  
Chemical Properties ◽  
Resonance Method ◽  
Alkyl Radicals ◽  
Spin Resonance ◽  
Physical And Chemical ◽  
Kinetics Of

The electron spin resonance method was employed to study the nature, concentration and kinetics of the disappearance under varying conditions of radicals produced in polyethylene by fast electron irradiation at 77°K. The predominant radical species at 77°K is the alkyl radical —CH 2 —ĊH—CH 2 —. On being warmed to room temperature it disappears rapidly, revealing a more stable un­identified radical. The kinetics of the decay at room temperature of both radicals was observed. Their stabilities were found to vary in polyethylene samples of differing physical and chemical properties. G values for these radicals are given. Comparison was made with spectra obtained under similar conditions with two pure paraffins and a pure olefin to evaluate the effect of crystallinity branching, molecular weight and unsaturation. In the olefin there is evidence for a build-up of allyl radicals due to the encounter of an alkyl radical with main chain unsaturation. This supports the view that alkyl radicals are mobile, and cross-linking occurs when two such radicals meet.

Shape of Alkyl Radicals by Electron Spin Resonance

Nature ◽  
1969 ◽  
Vol 222 (5199) ◽  
pp. 1123-1124 ◽  
Author(s):  
M. C. R. SYMONS
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Alkyl Radicals ◽  
Spin Resonance
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