摘要:

Sum rules are derived which relate moments ∫ ωn(dN/dω d2ṋn of the differential photon spectrum emitted by a classically moving point charge to the integral of the square of the apparent position, velocity or acceleration, as seen by the observer. Smoothing of the trajectory by means of a convolution with a functionf(τ), where τ is the observer's time, results in a filtering of the spectrum bybeing the fourier transform off(τ); this allows us to write filtered sum rules. Examples of applications of unfiltered and filtered sum rules to computer simulation of channeling radiation are presented.

ISSN:1042-0150    

DOI:10.1080/10420159108220735

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Single crystals of Iron, Nickel, Niobium and Stainless Steel (SS316) subjected to prolonged neutron irradiation in the Los Alamos Spallation Source for a period of one year have been studied using both small angle, and single crystal neutron diffraction. Small Angle Scattering show no evidence of any large radiation induced inhomogeneities in the pure metals, while regions of ∼ 65 Å diameter are found in the irradiated SS316. Combining the s.a.s. measurements with the single crystal diffraction data these regions are attributed to the formation of coherent precipitates of Ni-Cr. However, a low concentration of point defects (<2.5 at %) is introduced in all the materials by the irradiation process. No significant radiation induced dilatation of the lattice is found in any of the materials.

ISSN:1042-0150    

DOI:10.1080/10420159108220736

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We have studied the lilac spodumene through optical absorption and electron paramagnetic resonance measurements. The effects of increasing doses of γ-rays from60Co on the spectra were determined. The following absorption bands were analysed: 10500, 15600 and 21500cm−1assigned tod-dtransitions of Mn3+(G); 11000, 12000, 18600 and 22000cm−1assigned tod-dtransitions of Mn3+(L). TheGandLrefer to distinct octahedral sites, both tetragonally distorted with the axial Mn–O bonds extended (Jahn-Teller effect).

ISSN:1042-0150    

DOI:10.1080/10420159108220737

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The recovery of the electrical resistivity is reported for low-temperature electron-irradiated Au and dilute AuFe alloys. The concenration of Fe ranged from 123 to 2025 atppm. Samples have been irradiated to a range of doses extending from 0.56 to 16.8 × 1018cm−2. Two recovery stages that do not occur in pure Au are observed in the dilute AuFe alloys at 65 K and 110 K, respectively. The fractional recovery in both stages increases with increasing Fe-concentration and decreasing radiation induced Frenkel defect concentration. The 65 K stage can be assigned to the free migration of an interstitial-Fe causing radiation induced segregation. The other stage at 110 K can be attributed to the dissociation of complexes made up by interstitial and substitutional iron atoms. At higher temperatures the recovery in all dilute AuFe alloys indicates a segregation of the Fe atoms that recedes between 450 K and 600 K.

ISSN:1042-0150    

DOI:10.1080/10420159108220738

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Stress optical and EPR measurements are made on doped and X-irradiated single crystals of Rochelle salt in the paraelectric phase. With the nickel impurity no EPR signal is detected upto liquid nitrogen temperature. Manganese impurity forms two distinct types of paramagnetic centres. The spin Hamiltonian parameters are calculated and discussed for the Mn2+defect centres. The stress optical constant is found to change with the introduction of impurities and on X-irradiation of the crystals.

ISSN:1042-0150    

DOI:10.1080/10420159108220739

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Dilute iron-nitrogen alloys have been irradiated at low temperatures with electrons or neutrons to varying doses. In the temperature range above Stage III (T⩾ 200 K) a previously unknown family of small clusters composed of N interstitials and radiation-induced point defects, i.e. vacancies, could be resolved by means of a sensitive magnetic after-effect technique. Analysis of formation and dissociation kinetics of these clusters leads to nitrogen-vacancy binding energies between 0.08 and 0.5 eV, depending on cluster size. These relatively low values, together with further details of the precipitation kinetics, are shown to support the assumption of a two-interstitial recovery model.

ISSN:1042-0150    

DOI:10.1080/10420159108220740

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This paper deals with the characteristics of TLD-6LiF: Mg, Ti (TLD-600) to be used as an ultraviolet radiation dosimeter based on the photo-transfer thermoluminescence method. Thermoluminescent dosimeters were pre-irradiated with D2O-moderated252Cf neutrons instead of gamma rays in order to increase the growth efficiency of residual thermoluminescence to be transferred to UV irradiation. Thermoluminescent parameters, trap depth (E), frequency factor ([sgrave]) and kinetic order for neutron-irradiated TLD were studied by both glow curve shape analysis and variable heating rate methods. For the 203°C peak, theEvalues are 1.36 and 1.31 eV and [sgrave] values are 1.5 × 1013and 4.2 × 1012s−1respectively for these two methods. For the 263°C peak, theEvalues are 1.58 and 1.76 eV and [sgrave] values are 3.8 × 1013and 2.1 × 1015s−1respectively. Kinetic orders of both peaks were close to unity. The parameters obtained for peak 3 are comparable with that obtained by other investigators. The methodology of the optimal pre-annealing condition for UV radiation dosimetry is presented, and several TL characteristics in response to UV radiation are discussed.

ISSN:1042-0150    

DOI:10.1080/10420159108220741

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Optical absorption spectrum of cobalt doped MgNH4PO4· 6H2O (struvite) is investigated in UV-VIS-NIR regions. The spectrum in UV-VIS-NIR region is attributed to Co2+in octahedral symmetry whereas the IR spectrum is attributed to vibrations due to PO43-, NH4+and H2O. The following crystal field (Dq) and interelectronic repulsion (B, C) parameters are evaluated:Dq= 940cm−1,B= 870cm−1andC= 3970cm−1.

ISSN:1042-0150    

DOI:10.1080/10420159108220742

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Transient enhanced diffusion in boron-implanted silicon is interpreted as being due to the fact that during rapid thermal annealing a relaxation process takes place, associated with quasi-chemical reactions including defects. A simple analytical model makes it possible to describe the annealing mechanism on a microscopic scale in terms of reaction-diffusion processes. The measured dependences of the boron diffusion coefficient of the enhanced diffusion on time, temperature and implantation energy are satisfactorily explained.

ISSN:1042-0150    

DOI:10.1080/10420159108220743

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor