摘要:

When KN3and NaN3powders or single crystals are irradiated with γ-rays, X-rays or ultraviolet light at liquid helium or nitrogen temperatures and subsequently heated many thermoluminescent glow peaks are observed between 47 and 255°K. The KN3glow curves have been analyzed by four different procedures. Thus four values of the activation energy have been obtained for each peak, and these occasionally differ by as much as 50 per cent. However, the agreement is usually much better. One of these analyses, a numerical kinetics treatment employing a large computer has been used to determine the activation energies and the preexponential factors listed below for the more intense glow peaks from both KN3and NaN3. The temperature of the glow peak maxima in °K, the activation energy in eV, and the preexponential factor in sec−1, obtained for the five most prominent KN3peaks are: 109, 0.28, 1.0 × 1011; 123, 0.29, 2.3 × 1010; 142, 0.32, 7.7 × 1010; 211, 0.63, 1.5 × 1013; 245, 0.84, 1.0 × 1015. The corresponding values for the nine most prominent NaN3peaks are: 47, 0.067, 1.4 × 105; 52, 0.046, 102to 105; 117, 0.23, 6.6 × 107; 133, 0.26, 3.5 × 107; 175, 0.38, 2.0 × 109; 189, 0.38, 2.0 × 108; 205, 0.39, 3.7 × 106; 233, 0.37, 1.5 × 106; 255, 0.47, 6.2 × 106. A few of these NaN3glow peaks might possibly be related to previously observed ESR and/or color centers.

ISSN:0033-7579    

DOI:10.1080/00337577008243047

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The enhancement of diffusion by neutron irradiation has been investigated on a Cu-36 percent Zn alloy for various neutron fluxes and irradiation temperatures by means of in-pile measurements of electrical resistivity. For fresh samples the diffusion rate depends on temperature with an activation energy of 0.35 eV. During repeated irradiations the diffusion rate decreases and becomes nearly temperature independent. The variation of the concentration of interstitials and vacancies with irradiation time has been numerically calculated for various neutron fluxes, irradiation temperatures and sink concentrations. A comparison of the experimental and theoretical results shows that the point defects annihilate in fresh samples mainly by pair recombination and in samples which had been repeatedly cycled by pair recombination and at fixed sinks. Point defect clusters acting as sinks are created during the course of the irradiation as shown by electron microscope investigations. The radiation enhanced diffusion rate was found to depend on interstitials only, the activation energy of which was determined to 0.70 eV.

ISSN:0033-7579    

DOI:10.1080/00337577008243048

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The paper shows that the conclusions drawn from recent experiments on electron irradiation of gold at about 100° K should be reversed, i.e. that these experiments speakagainstthe free thermally activated migration of interstitials at the irradiation temperature. It is shown that this viewpoint is in agreement with several related experiments, which may all be interpreted by a dynamic propagation of crowdions over distances between 1000 Å and 2000 Å. At intermediate and high defect concentrations the dynamic propagation mechanism is suppressed.

ISSN:0033-7579    

DOI:10.1080/00337577008243049

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

ESR spectra of γ-irradiated frozen aqueous solutions of a number of organic compounds such as alcohols, ether, acetone and tetrahydrofurans have been examined in the presence and absence of mineral acids such as H2SO4. The presence of the acid is found to cause an intensification of the organic radical ESR spectra as compared with the acid free solutions. Also, the presence of the organic compounds in frozen aqueous H2SO4suppresses the formation of both H-atoms and SO4−radical ions. These results have been explained on the basis of reactions of the electrons and holes, or excitons, primarily formed by the action of radiation on the substrate ice.

ISSN:0033-7579    

DOI:10.1080/00337577008243050

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Pairs of copper samples—one for electrical resistivity, the other for Young's modulus measurements - were irradiated simultaneously at 120°K with 3 MeV electrons up to an integrated dose of 2 × 1020el/cm2. The effect of dislocation pinning and the bulk effect of point defects on Young's modulusEcould clearly be separated. The following relation between the bulk effectΔE/Eand the resistivity increase Δρ[Ωcm] was found:ΔE/E= −25 × 104× Δρ. Besides strong annealing in stages II and III (180–300°K) and some annealing between 300–500°K, stage V annealing (500–600°K) also was found. In stage III the resistivity annealed more than Young's modulus. whereas the converse occurred in stage V. These measurements are discussed in connection with the electron microsopical observation of point defect clusters after electron irradiation at 120°K and heating to room temperature.

ISSN:0033-7579    

DOI:10.1080/00337577008243051

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

On radiolysistris(acetylacetonato) cobalt(III) in aqueous solutions is found to get reduced by reaction with (1) hydrated electrons, (2) H atoms, (3) OH radicals and (4) C2H2OH radicals. The bimolecular rate constants for the first three reactions, determined by competition kinetics are: 4 × 1010, 2.3 × 109and 4.7 × 109M−1sec−1respectively. Absorption spectra of the irradiated solutions indicate the formation ofbis(acetylacetonato) cobalt(II) from reaction (1), but not from (3). The total cobaltous yield in air-free solutions is given byG(Co++) = 5.6 and 6.5 at pH 6.5 and 1 respectively. It appears that Geaq- ∽H+GoH∽ 2.8 in neutral solutions. Considerations of material balance for the primary yields of radiolysis of water suggest the possibility that the so-called independent H-atoms in neutral solutions are probably excited water molecules or ion-pairs.

ISSN:0033-7579    

DOI:10.1080/00337577008243052

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Undopedn-type GaAa was irradiated near 5 and 77 °K with electrons having incident energies between 0.46 and 1.30 MeV. The recovery of the electrical resistivity and the Hall coefficient upon annealing from 4 to 520 °K was monitored. Changes which occurred upon annealing below 200 °K could be reversed by ionizing radiation. A small amount of irreversible ionization-induced recovery was observed after irradiation near 5 °K. Major irreversible recovery stages were centered near 235 (stage I), 280 (stage II) and 520 °K (stage III). Recovery in stage I and II obeyed first order kinetics. The activation energies of stages I and II were determined as 0.72 and 0.83 eV, respectively. The carrier concentration changes per unit irradiation dose corresponding to the three recovery stages differed in their energy dependence indicating that the defects which are removed in stage III have the lowest threshold energy. The carrier concentration changes per unit irradiation dose corresponding to stages I and III were higher for irradiation near 5 °K than for irradiation near 77 °K.

ISSN:0033-7579    

DOI:10.1080/00337577008243053

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The electron-capture decay of a cobalt-57 atom triggers an Auger event resulting in the loss of several electrons from the molecule in which it is incorporated. The 14.4 keV Mössbauer emission conveys information regarding the chemical forms in which the daughter iron-57 is ‘stabilized’ within 10−7sec following electron capture. During this time the electronic relaxation occurs completely and several tens of electron volt energy is deposited in the molecule as a result of neutralization. We find that the ethylenediamine tetra-acetate,bis-salicylaldehyde tri-ethylenetetramine, acetylacetone, and indenyl chelates fragment in a large majority of events, resulting in the formation of degraded ionic Fe2+and Fe3+in the former cases and C9H7Fe+in the latter. On the other hand, highly conjugated compounds such as cobalt phthalocyanine and Vitamin B12escape fragmentation in 100 per cent of the Auger events.Tris-dipyridyl Co(III) perchlorate also escapes fragmentation in a majority of events. Apparently, the large amount of excitation energy deposited in the molecule as a consequence of charge neutralization is very rapidly (in less than 10−13sec) and efficiently dispersed through neighboring molecules. It is a novel phenomenon.

ISSN:0033-7579    

DOI:10.1080/00337577008243054

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

ISSN:0033-7579    

DOI:10.1080/00337577008243055

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

ISSN:0033-7579    

DOI:10.1080/00337577008243056

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor