摘要:

The application of single, plural or multiple scattering theories to the determination of defect dechanneling in channeling-backscattering disorder measurements is re-examined. A semiempirical modification to the method is described that results in making the extracted disorder and disorder distribution relatively insensitive to the scattering model employed. The various models and modifications have been applied to the 1–2 MeV He+channeling-backscatter data obtained from 20–80 keV H+to Ne+bombarded Si, GaP and GaAs at 50 K. and 300 K.

ISSN:0033-7579    

DOI:10.1080/00337577708233143

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Ion yield measurements are presented |of 2–10 keV helium ions scattered from a copper (100) face. The scattering angle is 30°. The results are explained using a charge transfer model originally proposed by the authors. The model takes into account Auger neutralization as well as ionization and neutralization resulting from a violent collision. The present results are compared with previous] experiments in which a primary atom beam was used. Within the experimental errors the results |of both experiments can be explained using the same charge exchange parameters. A second result of the present investigation is that more convincing evidence is given for the occurrence of neutralization during the violent collision by a non-Auger process. It is probable that this process, as well as the ionization process, results from an interaction between the helium particle and the copper L shell electrons.

ISSN:0033-7579    

DOI:10.1080/00337577708233144

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Secondary ion energy spectra have been measured for singly charged ions emitted from targets irradiated with 43 keV A+ions. Targets studied include the 3d transition metals (Sc, Ti, V, Cr, Fe, Ni) Cu and Zn, Zr, Al and Si and the compounds SiO2, Al2O3, NaCl, KCl. Energy spectra were measured in the energy range 1–600 eV. In several cases a peak in the energy spectrum in the region around 200 eV has been found. This is in addition to the usual low energy peaks in the region of 5–10 eV. In many cases the low energy peak was observed to decay steadily with irradiation time or to increase with oxygen pressure. In the case of the cleanest Zn spectrum, only the high energy peak can be detected. The data are discussed in relation to current models of secondary ion emission. We conclude that, in general, elemental metal targets which are clean are characterised by the high energy peak in the secondary ion energy spectrum. The slower ions emitted have been neutralised by electron exchange processes. The low energy peaks in unclean, partially clean, oxide coated or compound targets (NaCl, KCl) arise because the neutralisation of the slower ions is either not as efficient or is not possible. The secondary ion emission model of Blaise and Slodzian could account for the emission of ions from most targets.

ISSN:0033-7579    

DOI:10.1080/00337577708233145

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Implantation of helium ions into graphite has been found to produce surface features, which are discussed in terms of radiation damage as a function of depth into the material. Annealing and electron microscope studies show these surface features to be still well defined after annealing at 1500°C. The suggested interpretation is consistent with the large surface stress found in the surface layers of implanted materials.

ISSN:0033-7579    

DOI:10.1080/00337577708233146

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Powders of twelve alkali halides have been coloured in an electrodeless discharge. Due to the simultaneous production and bleaching of F centres, F aggregate centres could be produced in an adequate concentration. From their study it has been concluded that powders behave as deformed single crystals. It could also be shown from this study that the interaction between colour centres and dislocations is lattice dependent and varies regularly as cation changes from Li+to Rb+, and anion changes from F−to I−.

ISSN:0033-7579    

DOI:10.1080/00337577708233147

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Gamma irradiation of coumarin in aqueous solution gives fluorescent products proportional to radiation dose. Our earlier results showed that hydroxyl radical is mainly responsible for this effect. Fast neutron irradiation gave similar results but with a dose response of 0.4 relative to that of gamma dose response. This report gives the effect of adding boric acid to coumarin and irradiating with thermal neutrons in a nuclear reactor. The relative response to the high LET alphas and7Li recoils from10B(n, α)7Li reaction, is found to be approximately 8% as compared to gamma rays. This value is compatible with theGOHvalue for these heavy charged particles as compared toGOHof gamma rays in neutral aqueous solution.

ISSN:0033-7579    

DOI:10.1080/00337577708233148

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The effects of radiation damage in three crystalline organic materials have been investigated by electron microscopy.

ISSN:0033-7579    

DOI:10.1080/00337577708233149

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Three-dimensional, fine distributions of electron current density in a molybdenum crystal are examined by the many-beam dynamical theory of electron diffraction for electrons incident parallel to the principal zone axes. It is found that the two-dimensional distribution in the transverse plane oscillates along the depth direction, and that a highly localized distribution around the rows of atoms and an almost flat distribution appears alternatively with definite periods of depth. The effect of the localized current density on the damage production is discussed by introducing the “effective current ratio”,Jeffwhich is defined as the ratio of the local current density at the rows of atoms to the mean current density for electrons incident parallel to the zone axis. The valuesJefffor the incidence of 1 MeV electron are found to increase in the order of the (111), (001) and (110) directions. The energy dependenceJeffis also examined for the (001), (110) and (111) axial cases respectively.

ISSN:0033-7579    

DOI:10.1080/00337577708233150

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A simple diffusion model in which the plane is treated through a diffusion coefficient for Coulomb multiple scattering lower than that of a random medium and blocking is depicted as a specular reflection from the plane, has been developed to explain the occurrence either of feeding-in or blocking under different experimental conditions. Calculations were carried out for MeV protons in silicon crystals some microns thick, for angles of incidence on the {110} plane up to 1.5°. The results are in very good agreement with experiments of different authors. Transition between feeding-in and blocking of the kind observed along a star-pattern streak is also obtained. An elementary explanation of the results is given and some limitations of the model discussed. Monte Carlo simulations are used to obtain auxiliary informations on the processes occurring at the microscopic level.

ISSN:0033-7579    

DOI:10.1080/00337577708233151

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Aqueous suspensions of liveEscherichia Coli B (E. ColiB)bacteria cells were irradiated in the resting state under aerobic and anoxic conditions with 0.8 MeV electrons. Dried films of these suspensions were studied using infrared spectroscopy in the range from 4000 cm−1(2.5 Mm) to 700 cm−1(14.3 μm). The results show selective damage in that some molecular bonds are affected more than others. Changes observed include breakup of biopolymers, overall oxidation, nucleic acid base damage, and strand breaks in the DNA and RNA of cells. Oxygen is found to act as a powerful catalyst enhancing the amount of damage observed by a factor of 5 ± 2 over the damage observed under anoxic conditions. The minimum absorbed doses necessary to observe the onset of molecular alterations were about ten times higher than the D37dose for cell death in bacteria.

ISSN:0033-7579    

DOI:10.1080/00337577708233152

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor