Laser-induced birefringence in optical glasses

Laser-induced birefringence in silicate glasses is investigated. The birefringence is found at the boundary between the irradiated and unirradiated regions in the glass after long-term exposure to N₂ laser radiation (λ = 337 nm). Along with the stationary effect, a temporal (transient) change in the polarization of the probe beam is also observed, which arises only during UV irradiation and vanishes when the irradiation is over. The birefringence found is explained by the occurrence of anisotropy at the boundary between the irradiated and unirradiated regions of a glass due to a local change in the glass density in the irradiated region.     

Formation of the <Superscript>178<Emphasis Type="Italic">m</Emphasis>2</Superscript>Hf isomer in a natural mixture of hafnium isotopes irradiated by an intense γ quantum beam (experiment)

The results of an experiment on the production of the ^178m2Hf isotope by exposing a natural mixture of hafnium isotopes to an intense bremsstrahlung beam are reported. The sample under investigation was exposed to an electron beam with an energy of 30 MeV and current 200 μ A for 500 h. The spectrometric analysis of the irradiated sample using radiochemical methods for the separation of isotopes did not reveal ^178m2 Hf lines.     

Observation of a 〈100〉 mixed dumbbell at181HF in tungsten

TDPAC measurements were carried out in Tungsten foils and single crystals using implanted¹⁸¹Hf as a probe nucleus. After proton irradiation at 25 K the trapping of a defect at the Hf probe was observed, which lead to a quadrupole interaction frequency of _Q=354(5) MHz. The defect could be identified as a W self interstitial forming a 100 mixed dumbbell with a Hf impurity atom.     

Tuning the properties of tin oxide thin films for device fabrications

Tin oxide thin films were deposited on well cleaned glass substrates by thermal evaporation in vacuum and were annealed at 500?^°C in the open atmosphere inside a furnace for 90 min for promoting the sensitivity of the films. The X-ray diffraction studies revealed that the as-deposited films were amorphous in nature and the annealed films showed appreciable crystalline behavior. The annealed thin films were then irradiated using ⁶⁰Co gamma source. The radiation induced changes were then studied by X-ray diffraction, scanning electron microscopy, UV–vis spectroscopy and I–V characterization. The remarkable increase in the average grain size, the decrement in the energy band gap and resistivity due to the gamma irradiations up to a certain dose and the reversal of these properties at higher doses are the important observations. The large changes in the conductivity and energy band gap of the annealed thin films due to gamma irradiation make these films quite important device material for the fabrication of gamma sensors and dosimeters.     

The TDPAC study of quasicrystalline and T-phases

Time differential perturbed angular correlation (TDPAC) spectra of the quasicrystalline phase Al₇₉Mn₂₀Si₁ (800 ppm Hf) and the decagonal phase (T-Phase) Al₈₀Mn₂₀ (800 ppm Hf) were measured using the¹⁸¹Hf probe. It is obtained that the structure around the center in Mackay icosahedra in the decagonal phase seems to be distorted in comparison with that in the quasicrystalline phase.     

Effect of gamma ray irradiation on optical properties of Nd doped phosphate glass

The effect of gamma irradiation in the dose range of 5-500 kGy on the optical absorption and luminescence spectra of Nd doped phosphate glass is reported. The spectral absorption of this glass before and after gamma irradiation was measured in the spectral range 300-900 nm at room temperature using spectrophotometer and synchrotron beamline. Drastic increase in absorption was noted below 600 nm after gamma irradiation, which was dependent on the dose of irradiation. Additional absorption (AA) spectra of irradiated sample shows generation of two absorption bands below 600 nm, which finally became one very broad band peak with increased intensity at irradiation dose of 500 kGy. AA spectra also show the presence of negative peaks at the location of absorption peaks of Nd³⁺. Photoluminescence of Nd doped phosphate glass shows two strong bands which decreases to a very low intensity with a red shift after gamma irradiation. These results indicate that irradiation produces different kinds of defects in the glass material along with conversion of valence state of Nd³⁺ to Nd²⁺. This change was found irreversible at room temperature.     

Spectral,X-ray diffraction,surface morphological and thermal studies of gamma-irradiated potassium bis(oxalato)zincate(II)dihydrate

ABSTRACT

Potassium bis(oxalato)zincate(II)dihydrate was prepared and characterized. The sample was irradiated with ⁶⁰Co gamma rays up to 900?kGy. Infrared, Raman and photoluminescence spectra, X-ray diffraction pattern, surface morphology by AFM and SEM and non-isothermal decomposition of the complex were studied before and after irradiation. Spectral studies suggested significant radiation damage. X-ray diffraction studies showed reduction in unit cell volume and average crystallite size. Both unirradiated and irradiated samples of the complex belong to the hexagonal crystal system. Surface morphology of the complex changed upon irradiation. Thermal decomposition was enhanced.     

Investigation of radiosterilization feasibility of sulfamethoxazole by ESR spectroscopy

In the present study, the spectroscopic features of the radiolytic intermediates that were produced in gamma-irradiated (5, 10, 25 and 50?kGy) sulfamethoxazole (SMX) have been investigated by electron spin resonance (ESR) spectroscopy and the radiation sterilization feasibility of SMX by ionizing radiation was examined. Gamma-irradiated SMX exhibited a complex ESR spectrum consisting of 13 resonance lines where spectral parameters for the central resonance line were found to be g?=?2.0062 and ΔH_pp?=?0.6?mT. The radiation yield of SMX was calculated to be relatively low (G?=?0.1) by ESR spectroscopy and no meaningful difference was observed in the comparison of unirradiated and 50?kGy gamma irradiated SMX by the Fourier transform infrared (FT-IR) technique, confirming that SMX is a radioresistive material. Although SMX could not be accepted to be a good dosimetric material, the identification of irradiated SMX from the unirradiated sample was possible even for the low absorbed radiation doses and for a relatively long time (three months) after the irradiation process. Decay activation energy of the radical species, which is mostly responsible for the central intense resonance line, is calculated to be 45.15?kJ/mol by using the signal intensity decay data derived from annealing studies. Four radical species with different spectroscopic properties were accepted to be responsible for the ESR spectra of gamma-irradiated SMX, by simulation calculations. It is concluded that SMX and SMX-containing drugs can be sterilized by gamma radiation and ESR spectroscopy is an appropriate technique for the characterization of these induced radical intermediates during the gamma irradiation process of SMX. Toxicology tests should also be done for its safe usage.     

Electric field gradients at Ta in Zr and Hf inter-metallic compounds

Here we calculate the electric field gradient (EFG) at the nucleus of the substitutional Ta impurity site in Zr₂T and Hf₂T (T=Cu, Ag, Au, and Pd) C11_b inter-metallic compounds. We use the ab initio FP-LAPW method as embodied in the Wien97 code in a super-cell approach and include lattice relaxations around the impurity. Our results are compared with EFG values inferred from measurements of the quadrupole coupling constants at the ¹¹¹Ta probe in these compounds performed with the time differential perturbed angular correlation (TDPAC) technique. We also performed EFG calculations for the pure inter-metallic compounds. Through the comparison of theoretical and experimental EFGs in these cases, we elucidate the role played by the Ta probe in the TDPAC measurements of Hf and Zr compounds. Our results show that, although the EFGs at the Hf site are very similar to the EFGs at the Ta impurity, there is no direct correlation between the Zr and Ta EFGs.     

Effect of gamma irradiation on X‐ray absorption and photoelectron spectroscopy of Nd‐doped phosphate glass

X‐ray absorption near‐edge structure (XANES) and X‐ray photoelectron spectroscopy (XPS) of Nd‐doped phosphate glasses have been studied before and after gamma irradiation. The intensity and the location of the white line peak of the L₃‐edge XANES of Nd are found to be dependent on the ratio O/Nd in the glass matrix. Gamma irradiation changes the elemental concentration of atoms in the glass matrix, which affects the peak intensity of the white line due to changes in the covalence of the chemical bonds with Nd atoms in the glass (structural changes). Sharpening of the Nd 3d_5/2 peak profile in XPS spectra indicates a deficiency of oxygen in the glasses after gamma irradiation, which is supported by energy‐dispersive X‐ray spectroscopy measurements. The ratio of non‐bridging oxygen to total oxygen in the glass after gamma radiation has been found to be correlated to the concentration of defects in the glass samples, which are responsible for its radiation resistance as well as for its coloration.     

Zr-induced structural changes in Hf1−x Zr x O2 high-k thin films

The local symmetries around the Hf sites in thin films of Hf_1?x Zr _x O₂/Si(100) were probed using grazing incidence extended X-ray absorption fine-structure spectroscopy (EXAFS). The effects of the Zr incorporation on the local crystal symmetries were investigated using Hf L₃ EXAFS at the Beamline X23A2 of the Brookhaven National Laboratory. The Zr ratios in the various films were set to between 0.0 and 1.0. Significant changes in the local environment were observed for x = 0.25 or greater values. For x = 0.0, the film local structure around Hf sites remain in the equilibrium monoclinic phase as referenced from our previous studies on HfO₂ thin films on Si(100). When Zr is introduced, tetragonal symmetry around the Hf atom appears and becomes dominant at x = 0.63. Using the EXAFS theoretical simulations and non-linear least-square fit results, the fractions of the monoclinic versus tetragonal phases were identified in each film.     

Perturbed Angular Correlation of the stretched cascade in the decay of 180mHf using a digital spectrometer

We report on the measurement of the nuclear quadrupole interaction (NQI) at Hf sites using the nuclear probe ^180mHf in HfF₄·HF·2H₂O at 300 K by exploiting all possible start quanta in the stretched cascade with a digital Time Differential Perturbed Angular Correlation (TDPAC) spectrometer. With conventional spectrometers, multiple prompt start signals would paralyze the router. The gain in coincidence rate is about a factor of 5 compared to a conventional spectrometer using a single start only. With multiple starts ^180mHf is a promising new isomeric nuclear probe in TDPAC experiments. As an additional feature we implemented the possibility to measure up to four cascades simultaneously in order to save data collection time or to measure isobaric contaminations like ^111mCd and ¹¹¹In.     

Finely dispersed phases of <Emphasis Type="Italic">M</Emphasis>O(OH)<Subscript>2</Subscript> (<Emphasis Type="Italic">M</Emphasis> = Zr,Hf) oxyhydroxides

We discuss studies of new finely dispersed phases of zirconium and hafnium oxyhydroxides MO(OH)₂ (M = Zr, Hf) by means of X-ray diffraction, NMR, Raman scattering, IR spectroscopy, electronic microscopy and thermal analysis. It is demonstrated that these compounds and their precursors (lithium salts obtained by citrating) are isostructural. Hafnium oxyhydroxide is thermally more stable than its zirconium analog and decomposes at approximately 260°C.     

Ar离子辐照导致微球玻璃机械性能的变化

为研究离子辐照导致空心玻璃微球机械性能的变化,利用Ar离子辐照与空心玻璃微球组分相同的微球玻璃薄片,结合不同温度下的等时退火处理,采用纳米压痕测试方法研究了辐照前后玻璃机械性能的变化。测试结果表明:辐照后玻璃的硬度和模量均呈下降趋势,恢复阻力明显升高;退火后的未辐照样品硬度和模量呈上升趋势,恢复阻力在误差范围内没有发生变化; 退火后的模量呈下降趋势,恢复阻力呈下降趋势;在退火温度约为300 ℃时,辐照样品退火后的恢复阻力与未辐照样品基本相同。     

Effect of gamma-irradiation on thermal decomposition kinetics,X-ray diffraction pattern and spectral properties of tris(1,2-diaminoethane)nickel(II)sulphate

Tris(1,2-diaminoethane)nickel(II)sulphate was prepared, and characterised by various chemical and spectral techniques. The sample was irradiated with ⁶⁰Co gamma rays for varying doses. Sulphite ion and ammonia were detected and estimated in the irradiated samples. Non-isothermal decomposition kinetics, X-ray diffraction pattern, Fourier transform infrared spectroscopy, electronic, fast atom bombardment mass spectra, and surface morphology of the complex were studied before and after irradiation. Kinetic parameters were evaluated by integral, differential, and approximation methods. Irradiation enhanced thermal decomposition, lowering thermal and kinetic parameters. The mechanism of decomposition is controlled by R₃ function. From X-ray diffraction studies, change in lattice parameters and subsequent changes in unit cell volume and average crystallite size were observed. Both unirradiated and irradiated samples of the complex belong to trigonal crystal system. Decrease in the intensity of the peaks was observed in the infrared spectra of irradiated samples. Electronic spectral studies revealed that the M–L interaction is unaffected by irradiation. Mass spectral studies showed that the fragmentation patterns of the unirradiated and irradiated samples are similar. The additional fragment with m/z 256 found in the irradiated sample is attributed to S₈⁺. Surface morphology of the complex changed upon irradiation.     

X-ray absorption and emission spectroscopy at the Hf L1 edge of hafnium-(silicon)-oxide ultra-thin films

X-ray absorption and emission spectroscopic study at the Hf L₁ edge was applied to investigate the local structure around hafnium atoms in Hf(Si)O_x ultra-thin films, which are the most promising candidates for the high-k gate dielectric material of next generation CMOS devices. HfSiO_x showed an extra absorption above the Hf-L₁ threshold, which is not seen in HfO_x. HfSiO_x also had stronger Compton scattering peak in Hf-Lγ emission region, and smaller Hf-Lγ₂/Lγ₃ ratio, compared with those of HfO_x. These differences should be caused by partial replacements of hafnium atoms by silicon atoms as the second nearest neighbors of a hafnium atom.     

Geometric,stability, and electronic properties of gold-doped Pd clusters (Pd<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>Au, <Emphasis Type="Italic">n</Emphasis> = 3~20)

The structure, stability, and electronic properties of Pd _n Au (n = 3~20) clusters are studied by density functional theory. The results show that the clusters studied here prefer three-dimensional structures even with very small atom number. It is found that the binding energies of Pd _n Au clusters are higher than the corresponding pure Pd _n clusters with the same atom number. Most Pd _n Au clusters studied here are magnetic with magnetic moments ranging from 1.0 to 7.0 μ _B. The dissociation energies of Pd atoms are lower than the doped gold atom, that is the doped Au atom will increase the mother clusters stability and activity.     

Feasibility of radiation sterilization and dosimetric features of ampicillin: an electron spin resonance study

In the present work, it was aimed to identify radical species produced by gamma irradiation (3–34?kGy) of solid ampicillin, to determine its spectroscopic, dosimetric, stability and kinetic behavior, and to investigate feasibility of the radiation sterilization feature of ampicillin by using electron spin resonance (ESR) spectroscopy. ESR experiments were performed at low and high temperatures (130–400?K) to examine the characteristic properties of the radical intermediates that are produced in ampicillin by gamma radiation treatment. Unirradiated ampicillin presented no ESR signal but irradiated samples exhibited ESR spectra with four resonance peaks spread over a magnetic field range of 8?mT. The spectral parameters of the central resonance line of the spectrum are g?=?2.0044 and ΔH_pp?=?0.08?mT. An exponential growth function of the applied dose was found to describe best the experimental dose–response data and it was found that ampicillin did not exhibit the feature of a good dosimetric material as its ESR intensity was relatively weak even for the samples irradiated at high level of doses. G_mean value of gamma-irradiated ampicillin was found to be 4.6?±?0.9?×?10^?9?mol/J, which is very small compared to irradiated alanine solid sample. However, the discrimination of irradiated ampicillin from unirradiated one was possible even ～3 months after storage at normal conditions. The simulation calculations indicated that gamma irradiation created two different radical species in solid ampicillin. Decay activation energy of the radical species which is mostly responsible from central intense resonance line is calculated to be 55.6?±?3.2?kJ/mol by using the signal intensity decay data derived from annealing studies. It was concluded that ampicillin could be sterilized by gamma radiation and ESR spectroscopy can be used as a potential technique to monitor its radiosterilization process.     

Features of changes in the surface structure of K-208 glass under electron—proton irradiation

Changes in the surface structure of K-208 glass after single-time irradiation of its samples with 20-keV electrons and protons are studied using atomic-force microscopy. Irradiation is performed in a vacuum chamber under a pressure of 10^–4 Pa; the densities of the electron (? _e ) and proton (? _р ) fluxes are varied in the range of 10¹⁰–2.5 × 10¹¹ cm^?2 s^?1. Analysis of the samples irradiated in the case where the parameters ? _e and ? _р increased in a stepwise manner makes it possible to study the appearance, growth, and evolution of microscopic structures on their surfaces. The radiation-stimulated processes of defect annealing and the release and field diffusion of alkali metal ions are accompanied by crystallization of the irradiated glass layer, which gives grounds for the use of dislocation mechanisms for mass transfer in explaining the formation of microprotrusions on its surface. It is shown that the character of changes in the structure is determined by the values of the parameters ? _e and ? _р and the ratio between them. In particular, it is established that, in the case of electron— proton irradiation of the glass, electrostatic discharges begin to noticeably affect the formation of microprotrusions for ? _е > 3? _р .     

New neutron-rich nuclide185Hf

The unreported hafnium isotope¹⁸⁵Hf has been identified for the first time. Sources of¹⁸⁵Hf prepared by 14-MeV neutron irradiation of tungsten followed by radiochemical separation have been studied. The new activity was identified by following the time variation of the rays. The half-life of¹⁸⁵Hf has been determined to be 3.5±0.6 min. In addition, a new 164.5±0.5keV ray was found and assigned to¹⁸⁵Hf based on the measurements of transition energy and half-life.This work was supported by Academia Sinica