摘要:

In the low energy atomic collision of ε ≤ 0.1, the energy dissipation of projectile ion is mainly by the nuclear stopping. In this energy rangeZ-oscillation appears on ranges and range stragglings. In order to explain this osciallation from the viewpoint of molecular effect on interatomic potentials, an extended Hückel method is adopted for potential calculation. TheZ-dependence on interatomic potentials to describe respective atomic collisions is similar to that ofZ1-range oscillation. It suggests a possibility of molecular effect on theZ1-range oscillation.

ISSN:1042-0150    

DOI:10.1080/10420159008213025

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Computer simulations typically determine the particle-distribution function corresponding to a single-event point source. This distribution function contains all the information needed to determine the corresonding steady-state distribution. From the single-event point-source distribution one can also deduce the distributions resulting from plane and volume-homogeneous sources, both for single event and steady state. A formalism for making these deductions is developed, based on the observation that the distribution determined by computer simulation obeys the Boltzmann transport equation, and on the properties of the Green's functions solutions of that equation, particularly the consequences of space- and time-translation invariance. The treatment deals explicitly with a homogeneous target infinite in every direction, but is easily generalized to cases with boundary conditions, such as a beam bombarding a layered target in slab geometry.

ISSN:1042-0150    

DOI:10.1080/10420159008213026

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A theoretical model is developed to study the influence of radiation-induced microstructural evolution on the amorphization kinetics of intermetallic compounds. The amorphization mechanism is assumed to be the buildup to a critical level of defect complexes. A complex consists of a coupled interstitial-vacancy pair. It is shown that the process of amorphization under particle bombardment is obstructed in alloy systems in which interstitials exhibit a tendency to cluster. In these systems, interstitial clustering delays the buildup of complexes. Under electron irradiation, the complex concentration attains a very low level after high doses, and the crystalline-to-amorphous transition is inhibited down to fairly low temperatures. During heavy ion bombardment, cascade damage produces an enhancement of complex formation and the transition takes place. It is shown that the kinetics of amorphization under ion bombardment depends on temperature at low temperatures, where amorphization is mostly due to complex accumulation. On the other hand, the present analyses indicate that direct in-cascade amorphization becomes more important as the bombardment temperature increases. Zr3Al is used as a model system. The theoretical calculations yield good agreement with experimental results.

ISSN:1042-0150    

DOI:10.1080/10420159008213027

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The effects ofin-situelectron and ion bombardment in quartz are compared. Both types of irradiation readily induce the metamict transformation and, furthermore, do so in linear proportion over the entire range of their combination. The results suggest that the creation of oxygen vacancies is responsible for the metamict transformation in both cases.

ISSN:1042-0150    

DOI:10.1080/10420159008213028

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Thermoluminescence (TL) and ESR phenomena induced by X-ray irradiation of the mixed samples of K2SO4and alkaline earth metal sulfate (MgSO4or BaSO4) were investigated in terms of the reactivities and the crystallogrpahic properties. A high intensive TL resulted from the diffusion of a small amount of Mg2+into K2SO4crystals. The amount formed of K2Mg2(SO4)3, langbeinite, compound had a maximum at the stoichiometric composition. From the ESR measurements, SO−3radicals were found to be easily formed in the langebeinite by excitation. Both the TL and the ESR phenomena were hardly observed in the K2SO4–BaSO4system due to little diffusion of Ba2+with much larger radius than Mg2+. The results were mainly discussed on the basis of the radii of the component cations in these systems. In addition, the fundamental data as to the application to the ESR dosimetry were obtained.

ISSN:1042-0150    

DOI:10.1080/10420159008213029

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

K2Mg2(SO4)3samples showed a more intensive ESR signal corresponding to SO−3radical than K2SO4or MgSO4samples. A decrease of the ESR signal intensity was observed in K2Mg2(SO4)3samples with the concentration of doping La or Eu, and it was remarkable with Eu doping. In K3Na(SO4)2samples, the ESR signal intensity increased with the concentration of doped La and had a maximum at about 1 mol% La2(SO4)3, while it decreased with the concentration of Eu doping similarly to the K2Mg2(SO4)3sample. Thermoluminescence (TL) intensities in K2Mg2(SO4)3and K3Na(SO4)2samples increased with the concentration of Eu doping, with maxima at about 1 mol% and 10−2mol% Eu2(SO4)3, respectively. With La doping, the TL intensity kept a nearly constant value in the K2Mg2(SO4)3sample and decreased in K3Na(SO4)2sample. The TL and ESR phenomena in La- or Eu-doped K2SO4, MgSO4and Na2SO4samples were also investigated. Both the TL and the ESR behaviors were discussed on the basis of the differences in radius and charge balance between the constituent cations in the matrix and dopant.

ISSN:1042-0150    

DOI:10.1080/10420159008213030

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We present IR spectra of polyethylene films before and after irradiation with 1.5 MeV protons or 254 nm UV photons. By the study of the spectra of irradiated films, we get insight into the induced physical and chemical modifications. In particular phenomena as UV induced photooxidation and structural ion-induced changes are quantitatively reported.

ISSN:1042-0150    

DOI:10.1080/10420159008213031

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:1042-0150    

DOI:10.1080/10420159008213032

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Defects in both as-grown and neutron irradiatedn- andp-type epitaxially grown cubic silicon carbide (3C-SiC) on Si (100) substrates have been characterized electrically. Due to the lattice mismatch the SiC-Si interface has a large density of dislocations. Electronically active states associated with this interface are observed in thinn-type material. Thicker layers ofn- andp-type cubic SiC are free of electronically active deep levels. Deep Level Transient Spectroscopy (DLTS) measurements of neutron irradiated material indicate an electron trap at Ec-0.49 eV inn-type material and three hole traps at Ev + 0.18 eV, Ev + 0.24 eV, and Ev + 0.51 eV inp-type material. Resistivity measurements in conjunction with the DLTS studies indicate that most of the radiation induced defects are in the middle third of the 3C-SiC bandgap. Ninety percent of the neutron irradiation defects anneal at 350°C, indicating that 3C-SiC is a promising material for device operation at high temperatures and in radiation fields.

ISSN:1042-0150    

DOI:10.1080/10420159008213033

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Several conditions which result in instabilities and nonlinearities in the processes associated with the recombination of point defects are discussed.

ISSN:1042-0150    

DOI:10.1080/10420159008213034

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor