摘要:

Sputtering of isotopic (001), (011), and (111) Mo single crystals with 0.15–10 keV Ar ions at low fluences has been studied by means of computer simulation. Attention was given to the dependence of the preferential emission of light isotopes on ion energy and direction of incidence. It has been shown that the enrichment in light isotopes results mainly from a high contribution to sputtering of recoils of low generations which, in turn, correlates very closely with the crystal transparaency and accompanying channeling effects. At glancing incidence, the preferential emission of light isotopes is strongly affected by the surface channeling of bombarding particles.

ISSN:1042-0150    

DOI:10.1080/10420159908226991

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Ion beam irradiation of polyvinyltoluene (PVT) induces strong chemical and physical modifications. Using 50—300 keV proton, helium and nitrogen beams, at low doses, below 1012ions/cm2, dehydrogenation and molecular emission of CxHygroups occurs. At higher doses the irradiation induces surface roughness and density increase of the polymer. Main emitted species are H2, C2H2and C3H5. At high ion doses the polymer density may reach 195% of its initial value and the roughness may reach micron dimensions. The densification process is investigated as a function of the ion fluency and ion stopping power.

ISSN:1042-0150    

DOI:10.1080/10420159908226992

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Mössbauer spectroscopy was applied to study radiation damage in evaporated Fe layers irradiated with 209 MeV84Kr ions at room temperature. Significant differences have been shown between the Mössbauer spectra of the unirradiated and the irradiated samples. The increase of a nonmagnetic component of the spectra as well as a magnetic component around 270 kOe was observed due to the irradiation. The changes were also analysed using the hyperfine field distribution obtained from the spectra. The results can be interpreted as the formation and the increase of proportion of highly disordered phases in Fe layer due to irradiation with energetic heavy ions.

ISSN:1042-0150    

DOI:10.1080/10420159908226993

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The microreliefs of the fractured surfaces of non-irradiated low density polyethylene (LDPE) and gamma irradiated high density polyethylene (HDPE) “BULEN” are similar, but are obtained due to different microdestruction mechanisms determined by different interaction mechanisms of the macromolecular chains. The LDPE is characterized by low degree of co-operation of the sublevels of the superstructural molecular organization, high branching and high density entanglements of the macromolecular chains which are uniformly distributed in the amorphous regions and in the intercrystalline amorphous regions. The surface structures in the gamma irradiated HDPE represent areas with homogeneous distribution of the radiation-induced chemical crosslinking density νc,chwhich form lattices build up of macromolecular networks and are distributed predominantly in the intercrystalline amorphous regions. Obtaining such superstructural molecular organization in the irradiated polymer depends strongly on the state and structural organization of the initial non-irradiated polymer.

ISSN:1042-0150    

DOI:10.1080/10420159908226994

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Ranges and energy-loss up to 4.7 MeV/u28Si ions in Makrofol-G polymer have been determined using a nuclear track technique. Polyallyldiglycol carbonate (CR-39) detectors were calibrated using Al degraders to determine the degraded energy of28Si ions after passing through the different stacks of Makrofol-G placed in the staircase configuration. The mean ranges of28Si in Makrofol-G have also been determined at different energies between 1.0 MeV/u and 4.7 MeV/u. The experimental results are discussed and compared with the theoretical values obtained from four different computer codes.

ISSN:1042-0150    

DOI:10.1080/10420159908226995

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The behavior of luminescence emission of AlN ceramics under reactor and gamma irradiation has been studied within-situluminescence and thermoluminescence methods. A broad emission peak (around 370 nm), which had a different position for AlN samples with different oxygen concentration, was found. The intensity of luminescence emission has close relations with reactor power (fast neutron flux) and temperature. Influence on emission behavior from radiation defects (vacancies and interstitials) and intrinsic defects (oxygen-related defect complexes) was discussed.

ISSN:1042-0150    

DOI:10.1080/10420159908226996

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Electron paramagnetic resonance (EPR) spectrum of Cr3+ions doped ternary K2SO4-Na2SO4-ZnSO4glasses has been studied at different temperatures. The low field spectral resonance lines of the EPR spectra of Cr3+ions in K2SO4-Na2SO4-ZnSO4glasses are attributed to isolated Cr3+ions whereas the high field spectral resonance line is attributed to exchange-coupled pairs of Cr3+ions. The optical absorption spectrum of Cr3+ions doped glass shows two broad bands characteristic of Cr3+ions in octahedral symmetry. From the optical spectrum, the crystal field parameter (Dq) and the Racah interelectronic repulsion parameters (BandC) have been evaluated. From the EPR and optical spectral data, it is concluded that the site symmetry arround Cr3+ions is octahedral and the nature of bonding is predominantly covalent in nature.

ISSN:1042-0150    

DOI:10.1080/10420159908226997

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In the present paper, a theoretical approach has been made to the stability of color centers in microcrystalline powders of alkali halides. The diffusion of point defects from higher concentration region to lower concentration region may give rise to the unpinning of some of the pinned dislocations, whose interaction with the color centers may cause the capture of their electrons. The captured electrons may move with the unpinned dislocations and they may subsequently be transported to different trapping centers. This process may give rise to the decay of coloration in the microcrystalline powders. Considering the decay of coloration by the unpinning of dislocations, an expression has been derived for the coloration decay in microcrystalline powders of alkali halides. The decay of coloration is different for different alkali halide crystals and it is faster in the particles obtained by crushing the single crystals as compared to the particles of the same size obtained by cleaving the single crystals. The decay of coloration increases with decreasing size of microcrystals, increase with temperature of the crystals, decreases with increasing radiation dosage given to the crystals, and decreases with inclusion of dopants in the crystals. The coloration decay is faster in γ-irradiated crystals as compared to the electrolytically colored crystals. The dependence of coloration decay of microcrystalline powders on different parameters may be understood using the theory based on the interaction of unpinned dislocations with the color centers.

ISSN:1042-0150    

DOI:10.1080/10420159908226998

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor