Proton irradiation effects

Ta metal under proton irradiation Study of radiation effects of the Ta(p, n) W reaction in Ta foil, recording of emission spectra before and after annealing with metallic Ta absorber, and of absorption spectra before and after annealing W/W source... 

IRRADIATION EFFECT OF GAMMA-RAY ON THE PROTON-CONDUCTING POLYMER... 

Irie et al.28 obtained experimental evidence for the most stable conformation of the open form by using H NMR nuclear Overhauser effect (NOE) measurements. Irradiation of the protons in the NCH3moiety (3.79 ppm) produced positive NOEs of 10% at the H7 aromatic proton (7.49 ppm) and 19% at the H a olefinic proton. Irradiation of this a hydrogen produced a 12% enhancement of the NCH 3 proton, as illustrated in Figure 2.8. These observations indicated that the geometrical structure of the colored open form of spirooxazine is the TTC form. 

Hollerman, W.A. Goedeke, S.M. Bergeron, N.P. Muntele, C.I. Allison, S.W. Ila, D. Effects of proton irradiation on triboluminescent materials such as ZnS Mn. Nucl. Instrum. Methods Phys. Res. in press. 

The through-space distances involved in H H proximity determinations are quite small, and the effect decreases as the inverse of the sixth power of the distance, through space, between the protons. The usual observable enhancement is less than 20%. To increase the sensitivity, we use the NOE difference experiment, in which a conventional H spectrum is subtracted from a specific proton-irradiated spectrum this subtraction leaves only the enhanced absorptions. Under these conditions, a measurable effect can be expected between H nuclei over a distance of up to about 4 A (0.4 nm)t for example, the distance between 1,3-diaxial protons in the cyclohexane chair form is — 2.6 A. This procedure is a powerful tool in distinguishing among isomers, all of which should be available, if feasible, for NOE difference spectra (Fig. 4.54). 

The influence of high-energy (2.4 MeV) proton irradiation on the photoluminescence (PL), PL excitation and time-resolved PL spectra of InGaAs/GaAs quantum dots (QDs) is reported. The effect of irradiation on the PLE spectra is mainly attributed to a Fermi level shift towards the center of the gap. TRPL measurements show an evidence of carrier tunneling out of the excited QD states to adjacent defects. The ground level remains unaffected by the defects, at least up to a certain dose. Our considerations show that the dots very probably expulse radiation defects. 

Shibamoto H, Kitao T, Matsui H, Hasegawa M, Yamaguchi S and Kimura A (2001), Effect of nickel on irradiated hardening and microstructure evolution of proton irradiated Fe-Cu alloys . Effects of Radiation on Materials 20th International Symposium, Rosinski S T, Grossbeck M L, Allen T R and Kumar A S, eds, ASTM STP1405, American Society for Testing and Materials, West Conshohocken, PA, 722. 

The NMR techniques were also used to analyze different structural, surface reactions, reaction mechanisms, and other aspects related to the surface chemistry of silicas. For instance. Brunet et al. (2008) studied the electron irradiation effects on controlled-pore borosilicate glasses (CPGs at 8 and 50 nm in pore size, 96% Si02 and 3% B2O3) using multinuclear solid-state NMR technique. H MAS NMR was used to study the surface proton sites. They showed that the irradiation leads to a dehydration of the material. The observed variation of the Q4, Q3, and Q2 species from H- Si CPM AS spectra showed an increase of the surface polymerization under irradiation, implying in majority a Q2 to Q3/Q4 conversion mechanism, and CPMAS measurements exhibited an increase in... 

Rather soon after the nuclear magnetic reasonance (NMR) method was applied successfully to solid state physics, NMR was applied to the study of physical properties of polymers. To the best of our knowledge, a short paper by Wilson and Pake published in 1952 on the two-component structure of the proton NMR spectrum of polyethylene was the first paper in the field of NMR application to polymer science After that, many papers of NMR studies in polymer physics were published and many novel informations concerning molecular motions and structures of polymeric materials were presented. Recent advances in hardware of instrumentation of NMR measurement opened its application even to the medical and tomographic field Electron paramagnetic resonance (EPR or ESR), on the other hand, was applied to polymer science in the middle of the 1950s in the studies of polymerization and irradiation effects and its application to molecular motion study was established in the first half of the 1960s. 

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