Piezoelectric properties of crystals of some protein aminoacids and their related compounds

Growth of single crystals of some protein aminoacids and synthesis and growth of single crystals of their related compounds are reported. The temperature dependence of the integrated piezoelectric response of the single crystals grown was studied in the temperature range 120–320 K. The specific features in the temperature dependence are shown to be due to the enhanced damping of elastic vibrations in the crystals, which originates from the elastic vibrations being coupled to thermally activated rotation of the CH₃ and NH₃ molecular groups.     

Thermally stimulated effects in dielectrics and their application to radiation dosimetry

Certain dielectric materials show transient phenomena on heating following X- or γ- irradiation. There are three related phenomena which display the same pattern of behaviour, (a) thermoluminescence (T.L.); (b) thermally stimulated conductivity (T.S.C.); (c) exoelectron emission (T.S.E.).

The physics of these thermally stimulated effects is discussed and the development of dosemeters utilising them is described. So far only T.L. is used in a commercially available dose measuring system. Dosimetry using T.S.C. and T.S.E. is still at the research stage.     

Luminescence properties of common glasses for application to retrospective dosimetry

Seventeen domestic and scientific glass specimens were investigated for thermoluminescence (TL) properties suitable for application to retrospective population dosimetry. Usefulness for retrospective dosimetry was initially judged by the presence of well-defined TL glow peaks and the absence of irradiation-independent luminescence. Of particular interest were TL glow peaks having relatively low trap depths, to prevent significant natural dose accumulation. Minimum useful trap lifetimes would be in the order of weeks. Surveys were undertaken to observe the TL and optically stimulated luminescence (OSL) behaviour of each sample. Most samples showed identifiable TL, with Pyrex in particular, and samples from a jar, a lampshade, and opaque blue beads all showing well-defined TL glow peaks with sensitivities that were not significantly affected by prior irradiation and heating of the sample. Kinetic analysis of these samples showed that their TL emission originates from traps with suitable stability for retrospective dosimetry. It is concluded that, while some glass samples show promising results, the inherent variability of an amorphous substance such as glass means that the suitability of each sample must be determined on a case-by-case basis.     

Optical properties of sub-wavelength dielectric gratings and their application for surface-enhanced Raman scattering

We fabricated and measured the far-field optical properties of a sub-wavelength Si₃N₄ (silicon nitride) two dimensional grating. Frequency-dependent transmission measurements from a white-light source revealed that both transverse magnetic (TM) and transverse electric (TE) modes were excited on the grating. We determined the dispersion relations of the modes by tilting the sample with respect to the incoming light beam and measuring the frequency shift of the absorption features. By comparing to a simple model, we determined the effective refractive index for the TM and TE modes and the geometrical constants for the grating. This information enables gratings with desired optical properties to be designed and fabricated. The application of the sub-wavelength grating for surface-enhanced Raman scattering (SERS) is demonstrated.     

Optical properties of the surface transition-metal structures in fluoride ionic crystals and peculiarities of their formation during thermal diffusion

The possibility of forming surface films with an elevated concentration of an impurity metal during high-temperature diffusion has been analyzed for a wide series of ionic crystals: LiF with Co, Ni, Mg, Ca, Ba, and Sr impurities; NaF with Co, Mn, Mg, Ca, and Sr; MgF₂ with Co and Ni; and CaF₂ with Co. It is established that films are formed only on alkali halide crystals with impurities of transition metals and are not formed on alkaline earth fluorides with transition metals, as well as on alkali halide crystals activated with other divalent cationic impurities. The dynamics of the increase and decrease in the intensity of centers related to impurity-vacancy dipoles during thermal diffusion is shown. The mechanisms of film formation are explained in terms of the features of growth and structure of ionic crystals with cationic impurities and on the basis of isomorphism rules.     

Magnetic properties of some Cr-Ga intermetallic compounds

Magnetic susceptibility measurements in the range 10 – 300 K on the compounds Cr₃Ga, CrGa, Cr₅Ga₆ and CrGa₄ are reported here. All except CrGa₄ appeared to be Pauli paramagnetic, but CrGa₄ appeared to be basically diamagnetic with a parasitic weak ferromagnetic component.     

Optical properties and electronic structure of BiTeCl and BiTeBr compounds

Optical properties of BiTeCl and BiTeBr compounds with a strong Rashba spin–orbit coupling are studied in the 0.08–5.0 eV range using the optical ellipsometry method. Fundamental characteristics of the electronic structure are obtained. Similarly to BiTeI, spectra of the imaginary part of dielectric permittivity constant ε₂(E) in the energy interval between the plasma edge and the threshold of an intense interband absorption (0.7 eV in BiTeCl and 0.6 eV in BiTeBr) display a fine structure of electronic transitions at 0.25 and 0.55 eV in BiTeCl and 0.20 and 0.50 eV in BiTeBr. These features are assigned to electronic transitions between the bulk conduction zones split by the Rashba spin–orbit interaction. The parameters of the electronic structure of BiTeCl and BiTeBr are compared with the BiTeI compound that was studied earlier. In the BiTeCl–BiTeBr–BiTeI row, the absorption edge and main features of the fundamental absorption exhibit a shift to low energies.     

Switching and memory properties of some crystalline layer compounds

La Rivista del Nuovo Cimento (1971-1977) -     

On the optical properties of some layer compounds

The paper deals with the optical properties of single crystals near the fundamental absorption edge of the following layer compounds: Sn S_x Se_2−x (where 0 x 2), ZrS₂, ZrSe₂, TiS₂ and CdI₂. The dispersion curves were determined from the transmitted interference fringes in the range between 0.5 and 3.5 μm. Energy gaps were found to be due to phonon assisted indirect transitions. Birefringence data are also given for a number of crystals in the visible region.     

Optical and electrical properties of some sulphates doped with cobalt

Doubly ionized cobalt ion which has a ⁴F ground state exhibits several optical bands in orthorhombic sulphates. In view of the low symmetry, many degenerate states split and at low temperature (77°K) well resolved bands have been observed which enable the detailed calculation of the crystal field parameters in orthorhombic symmetry.Electrical conductivity measurements in pure potassium and ammonium sulphates show only the extrinsic unassociated region while in cobalt doped crystals, extrinsic as well as association regions are observed. Three distinct regions with slopes 0·86, 1·2 and 0·5 eV are obtained in cobalt doped K₂SO₄.X-irradiated pure crystals give two prominent bands at 2200 and 3300 Å which are attributed to SO₃^? and SO₂^?. Divalent cobalt doped crystals give additional bands at 2100 and 3100 Å. These bands are attributed to Co⁺ in different surroundings. Three ESR lines with ‘g’ values 2·042, 2·02 and 2·004 are obtained in support of the assignments.     

Optical properties of Eu3+ and Ho3+ in fluoride glasses

Conclusions Emission and excitation spectra as well as the lifetime and the Judd-Ofelt parameters were determined for the different sites occupied by Eu³⁺ ions in a fluorzirconate glass. As has been observed in borate glasses, the Ω₄ parameter increases with the excitation energy of the⁷F₀→⁵D₀ transition, while Ω₄ is nearly constant [5, 6]. These parameters are lower than in borate glasses by a factor of close to 3. The optical properties of the Eu³⁺ ions in the studied glass appear to be dominated by only one class of sites; however, the presence of a second class of sites is possible. Efficient energy transfer from Eu³⁺ to Ho³⁺ is observed, but the energy transfer parameter does not depend appreciably on the excitation wavelength. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 4, pp. 185–190, July–August, 1995.     

Luminescence properties of biotite relevant to dating and dosimetry

Biotite mineral grains from granitic rocks were subjected to luminescence studies with optical and thermal stimulation. Moderate thermoluminescence (TL) signals and weak optically stimulated luminescence (OSL) with blue-green light stimulation were detected after 50 Gy beta irradiation. No detectable infrared-stimulated luminescence (IRSL) was observed for natural and laboratory beta-irradiated samples. TL peaks at 118, 300, 360 and 480 °C can be identified from laboratory-irradiated samples. The 360 °C TL peak saturates at a higher dose than quartz, but shows significant anomalous fading after 80 days stored at room temperature. The potentials and problems for biotite used as a natural dosimeter are discussed.     

OSL properties of NaCl relative to dating and dosimetry

The luminescence properties of NaCl are discussed. Attention is focussed predominantly upon the optically stimulated luminescence (OSL) signal (UV emission) of NaCl (420–560 nm stimulation). The results from experiments relevant to geological dating applications, such as signal resetting, dose response and thermal stability, are described. The behaviour of the OSL signal observed was found to be favourable for dating, with both the thermal stability and dose response suggesting a range of at least 10 ka. Signal resetting via optical exposure was found to be extremely rapid and no evidence of either thermoluminescence or OSL signals was found following re-crystallization. The potential for dating natural salt deposits, as found in various arid environments, appears to be good.     

石墨烯等离激元的光学性质及其应用前景

石墨烯等离激元由于其独特的电学可调性、本征低衰减以及局域光场高度增强等特性, 引起了广泛的关注并迅速成长为一门新的学科分支--石墨烯表面等离激元光子学. 本文介绍了石墨烯等离激元的一些基本性质, 包括色散关系、局域的等离激元和传导的等离激元以及石墨烯等离激元对其周边介电环境的敏感性等. 在此基础上, 进一步介绍了石墨烯等离激元在太赫兹到中红外频段的应用, 比如有源光调制器的一些功能器件和增强的红外光谱探测等.     

Optical properties of mouse biotissues and their optical phantoms

The optical characteristics of a barrier discharge in a mixture of heavy water vapor with argon in the wavelength region 200–315 nm are presented. The dependence of the radiation intensity of the OD (A → X) band at λ = 309 nm on the partial pressure of the D₂O vapor is studied, the mechanism of hydroxyl formation in the plasma is considered, and optimal compositions of pollution-free and inexpensive mixtures based on Ar-D₂O are determined for application in UV lamps, which are promising for use in photomedicine.     

磁驱动准等熵压缩下单晶氟化锂的光学特性

以阳加速器和PTS装置为驱动源,开了展单晶氟化锂(LiF,通光方向［100］)窗口材料在准等熵压缩下的光学特性实验研究。应用全光纤激光多普勒探针系统(DPS,激光波长1550 nm)同时测量了Ly12铝材料电极加窗和未加窗的后界面速度历史,结合窗口材料修正方法获取了单晶氟化锂窗口材料在实验条件下折射率随密度的变化和界面粒子速度修正因子。每次实验可获取窗口材料样品的连续加载历史数据,进而处理得到LiF窗口材料在近50 GPa准等熵压力范围内的修正因子。结合拟合的线性关系,进一步处理获得了在实验过程中折射率随密度的变化。将这些实验结果与D.E. Fratanduono, Y. Ma, B.J. Jensen的对应数据比较,其中与光子多普勒测速系统 (PDV, 1550 nm)测量结果基本相符,不确定度与多次冲击实验得到的结果相当。     

磁驱动准等熵压缩下单晶氟化锂的光学特性

以"阳"加速器和PTS装置为驱动源,开了展单晶氟化锂(LiF,通光方向[100])窗口材料在准等熵压缩下的光学特性实验研究。应用全光纤激光多普勒探针系统(DPS,激光波长1550nm)同时测量了Ly12铝材料电极加窗和未加窗的后界面速度历史,结合窗口材料修正方法获取了单晶氟化锂窗口材料在实验条件下折射率随密度的变化和界面粒子速度修正因子。每次实验可获取窗口材料样品的连续加载历史数据,进而处理得到LiF窗口材料在近50GPa准等熵压力范围内的修正因子。结合拟合的线性关系,进一步处理获得了在实验过程中折射率随密度的变化。将这些实验结果与D.E.Fratanduono,Y.Ma,B.J.Jensen的对应数据比较,其中与光子多普勒测速系统(PDV,1550nm)测量结果基本相符,不确定度与多次冲击实验得到的结果相当。