摘要:

The influence of the surface topography on the polar angular distributions of secondary electrons emitted in Ar+(and Xe+)-Al collisions was studied. After each set of experiments, carried out in controlled bombardment conditions, the surface target was viewed by scanning electron microscope. Some models were elaborated to schematize the main structures observed. Under normal incidence, continuum background and Al L23VV Auger electron polar angular distributions were not modified by the topography and closely followed a cosine law which is that expected from a flat surface for electrons generated inside the crystal. This result was in agreement with the angular distributions calculated taking into account different structured surface models. For Al L23MM Auger electrons, experimental angular distributions as a function of the emission polar angle Θ, either were near a constant law or followed a decreasing law depending on the irradiation conditions. The N(Θ) curves calculated from the models showed that the isotropic angular distributions obtained for electrons generated outside the crystal from a flat surface could be strongly modified by the surface topography. These calculated curves reasonably agree with the different experimental distributions obtained from various surface topographies.

ISSN:0033-7579    

DOI:10.1080/00337578608208715

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Colloids can be formed much more easily in microcrystalline powders than in single crystals. They can be formed at lower and lower temperatures with decreasing particle size of the powders. Here, the particle size dependence of spontaneous colloid growth in electrodeless discharge is reported. It is shown that adequate concentration of colloids can be formed during lower and lower discharge times with decreasing particle size of the powders. The ease of colloid growth in finer particles is attributed to the increase of dislocations, which are the nucleation sites for the aggregation of F centers. It is further shown that addition of K (potassium) impurity decreases the observed ease in these powders.

ISSN:0033-7579    

DOI:10.1080/00337578608208716

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Radiation damage induced in natural fluorapatite and artificial sodium silica glass by fission fragments, alpha decay and electron irradiation has been studied by optical absorption spectroscopy of the respective color centers as a function of the radiation dose. Relative production efficiencies obtained are ∼3 × 10minus;7for alpha/fission in apatite, ∼3 × 10minus;5for alpha/fission in glass, ∼20 for electrons/alpha in apatite and ∼2 for electrons/alpha in glass, respectively. The values obtained for alpha/fission are orders of magnitude lower than values calculated from a purely collisional model. Moreover, absorption spectroscopy of defects in natural apatite is proposed as, a new (alternative to the fission track) method for the determination of mineral cooling ages.

ISSN:0033-7579    

DOI:10.1080/00337578608208717

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Energy loss straggling of protons (atomic and molecular beams) and He ions in gold has been measured in the region of the stopping power maximum with a high resolution electrostatic analyser. The results are compared with the predictions of Bethe-Livingston and Lindhard-Scharff theories. Contributions from additional stragglings are investigated in solids, where they are of practical interest.

ISSN:0033-7579    

DOI:10.1080/00337578608208718

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The kinetics of irradiation-enhanced growth of precipitates in solid solutions is investigated under conditions where the mass transfer is effected by mobile impurity-vacancy or impurity-interstitial complexes and the characteristic timet1of solution depletion is much larger than the timet0of establishment of quasi-stationary concentrations of intrinsic point defects. Under these conditions the system of four balance equations governing the concentrations of vacancies (Cv), interstitials (Ci), impurity atoms (Cl) and complexes (Cjl) (j=v, i) splits into a system of two equations governingCv,Ciand another system of two equations governingClandCjl. These systems are solved in the case of volume-averaged concentrations as well as by taking account of their inhomogeneous distributions. In the latter case the radiusRiof a spherical precipitate grows asRi(t)={const[1—exp(—τ/t1)]}½, where τ=t−t0andt1∼g−½, g being the generation rate of Frenkel pairs. The temperature dependence of the growth rate is described by formula (102).

ISSN:0033-7579    

DOI:10.1080/00337578608208719

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The formation of radiation-induced centres on irregular nodes is considered by means of potential curves in configuration coordinates. The results of the study of radiation effects on paramagnetic centres in silicate and quartz glasses at helium temperatures are described on the basis of a relationship between the dispersion of potential states and tunnelling.

ISSN:0033-7579    

DOI:10.1080/00337578608208720

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Monocrystalline and polycrystalline samples of BaFe12O19have been irradiated by 35 MeV/A krypton-ions to doses close to 1018ions.mminus;2and investigated by high resolution electron microscopy (HREM). The study has been devoted to the induced structural changes in the low energy range of the ions: 0 ≤E<0.9 GeV. Besides the amorphous transformation of the target in the heavily irradiated zone, some fragments were found to exhibit three main types of superstructures identified asa√3 ×a√3,a√3 ×a, and 2a× 2a. They have been explained on the basis of local atomic orderings probably due to the difference in strain between the amorphous and the crystalline parts of the sample.

ISSN:0033-7579    

DOI:10.1080/00337578608208721

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The temperature dependenceY*(T) of ion-bombardment-induced photon emission from sputtered species of a polycrystalline copper target is measured under conditions in which there is a pronounced increase of the sputtering yieldYat elevated temperatures. The dependenceY*(T) has been found to be qualitatively different for the optical lines of the neutral and ionized sputtered atoms. The dependencesY*(T) for the CuI lines are similar to the dependenceY(T), whereas the CuII line intensity is practically independent of the target temperature. The dependences of the photon emission for the CuI and CuII lines on ion incidence angle have also been found to be very different. The results obtained are discussed in terms of existing models for atomic excitation in sputtering.

ISSN:0033-7579    

DOI:10.1080/00337578608208722

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This study compares thein vitrocharacteristics of laboratory prepared thermochemical intermediates of ADU and uranium oxide produced at Australian uranium mines. All uranium oxide examined by batch dissolution behaved as two discrete fractions; the first a highly soluble (Class D) whose magnitude correlates with the total product sulphate concentration and a second fraction composed of soluble and suspended material. The dissolution of uranium by the batch method appears highly dependent on experimental procedure, invalidating interpretation ofin vitrobatch procedures in terms of dissolution half-time. It is suggested that the temperature of form ation may determine the degree of dissolution of the second fraction in ionic media. The proportions of the components in saline is predicted by a model given the saturation concentration of the soluble species and the fraction of suspended material.

ISSN:0033-7579    

DOI:10.1080/00337578608208723

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The defect levels produced in undoped p-type germanium by irradiation with 1.5 MeV or 2.0 MeV electrons and the annealing behaviour of the levels were studied by the DLTS technique. The positions of the trap levels, their concentrations and the cross sections for hole trapping of these traps were determined and the variation of the introduction rates of the traps with the energy of irradiation is reported. The level located at Ev+0.22 eV should be ascribed to a divacancy-oxygen complex and the Ev+0.31 eV levels to a defect-containing oxygen with regard to the effects of electrically inactive impurities. From the results of annealing under reverse or forward biases, the defect associated with the Ev+0.31 eV level is considered to be annealed by an ionization- enhanced mechanism.

ISSN:0033-7579    

DOI:10.1080/00337578608208724

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor