Determination of the Exciton Binding Energy Using Photothermal and Photoluminescence Spectroscopy

In this paper, experimental photoluminescence (PL) and piezoelectric photothermal (PPT) spectra of selected II–VI binary crystals are presented and analyzed. The quantitative analysis of the photothermal spectra was performed using a modified and extended Jackson–Amer model. The values of the bandgap energies of investigated semiconductors were computed from the PT amplitude and phase spectra. From the temperature dependence of the exciton emission so-called “excitonic energy gaps” have been determined. It follows from the theory that the exciton binding energy is the difference of these two values of energy gaps derived from PPT and PL spectroscopy.     

Absorption and Circular Dichroism Spectra of Bi12SiO20<Nd> Crystals

The absorption and circular dichroism spectra of Nd-doped Bi₁₂SiO₂₀ crystals were measured in the range 10000 to 20000 cm^–1. The spectra showed electronic transitions related to only one type of Nd-related center: Nd substituting for Bi in position with symmetry C ₁. The bands due to the transitions from the first Stark component of the ground state to Stark components of excites states (⁴ I _9/2 ⁴ G _5/2, ⁴ I _9/2 ² G _7/2, and ⁴ I _9/2 ⁴ G _7/2) were analyzed in detail. The dipole strength D _0k , rotatory power R _0k , and anisotropy factor G _0k of these transitions were calculated. The intensities of transitions to Stark components were shown to vary by more than one order of magnitude within an excited-state multiplet. The anisotropy factors of the ⁴ I _9/2 ² G _7/2 and ⁴ I _9/2 ⁴ G _7/2 transitions, allowed in the magnetic dipole approximation, are, on the average, larger than that of the ⁴ I _9/2 ⁴ G _5/2 transition, which points to a significant contribution of the magnetic moment (<>²) to the total intensity of the transition.     

Investigation of Permittivity Dispersion in the Infralow-Frequency Band by Time-Domain Dielectric Spectroscopy

The transient-current method of time-domain dielectric spectroscopy, used to investigate the dispersion of the dielectric parameters of materials in the 10^–4–1 Hz frequency band, and apparatus based on it, are considered. A program is developed for the mathematical processing of the results of an experiment using the numerical Fourier transformation method employing cubic splines for approximation, interpolation and extrapolation of data. The frequency spectra of ' and ' of certain solid materials are presented.     

Accurate Formulation of Faraday,Magnetic Circular Dichroism (MCD) and Kerr Effect of Light in Ferroelectromagnet

The Faraday, magnetic circular dichroism and Kerr effects are three important magneto-optic effects. They are significant in fundamental science and applications. Presently, scientists in this field believe that Faraday and Kerr effects are caused by the difference in real parts of the refractive indices of the magnetic crystal for left-and right-circularly polarized light and that magnetic circular dichroism is caused by the difference in the imaginary parts of the refractive index (absorption) of the magnetic crystal for left-and right-circularly polarized light. However, the derived equations for these effects are approximate only. In our paper we obtain accurate formulations for these effects and find that there are mistakes in the present conclusions with respect to the above-mentioned effects. The precise equations and conclusions from our derivation are presented.     

激光辐照40Cr钢组织结构的穆斯堡尔谱分析

４０Ｃｒ钢试样经不同热处理后在空气中用ＣＯ２连续激光束进行辐照，以穆斯堡尔谱学研究试样在辐照后的组织结构变化。试验结果表明，调质预处理后再进行激光辐照的试样，不仅残作产奥氏体含量较低，而且其中碳的含量最低。     

Observation of Combined Ferromagnetic/Paramagnetic Phase in Ga1?xMnxAs by Magnetic Circular Dichroism

Magnetic properties of a series of Ga_1–xMn_xAs layers with different Mn and hole concentrations has been studied by measuring magneto-absorption and magnetic circular dichroism (MCD). We first focus on comparing the MCD spectra of samples with unambiguous ferromagnetic or paramagnetic magnetization. We then investigate MCD in a sample with parameters between these two extremes, and interpret the observed behavior in terms of the coexistence of ferromagnetic domains and paramagnetic regions that may result, for example, from inhomogeneities in the sample caused, e.g., by compositional or doping fluctuations.     

Investigation of the thermo-stimulated surface segregation in the ternary Co-Cr-Mo alloy by means of Ionization Spectroscopy

Ionization Spectroscopy has been used to study thermo-induced surface segregation in the near-surface region of the ternary Co-Cr-Mo alloy. For the non-annealed alloy the Mo atoms preferred segregation in the outermost layers and Cr atoms segregation in the underlying layers of surface was observed at room temperature. Heating of the alloy promotes increasing of Co concentration and decreasing of Mo concentration in the near-surface region. For the annealed alloy the insignificant Mo atoms segregation on the outermost layers and enrichment with Co and Cr atoms in underlayers are displayed. The present results are compared with several theories of segregation.     

Investigation of Coupling Strength at Non-Central Interaction of Railcars

Strength of Materials - The strength of the coupling device under the action of operating loads with regard to the non-central interaction of two cars is defined. When longitudinal force is...     

Soft X-ray Magnetic Circular Dichroism and Photoemission Studies of II–VI Diluted Ferromagnetic Semiconductor Zn1−x Cr x Te

The electronic structure of the Cr ions in Zn_1−x Cr _x Te (x=0.03 and 0.15) has been investigated using X-ray magnetic circular dichroism (XMCD) and photoemission spectroscopy. Magnetic-field (H) and temperature (T) dependences of the Cr L _2,3 XMCD spectra well corresponded to the behavior of the magnetization measured by a SQUID magnetometer. The line shape of the Cr L _2,3 XMCD spectra was independent of H,T, and x, indicating that the ferromagnetism was originated from the same Cr electronic states independent of Cr concentration. The Cr 3d partial density of states (DOS) showed a peak at the top of the valence band but there was no DOS at the Fermi level, corresponding to their insulating behaviors.     

Exciton photo-luminescence of GaN bulk crystals grown by the AMMONO method

GaN in form of microcrystals were obtained using a new technique—the AMMONO method. The growth was performed at relatively low temperature and pressure conditions, in comparison with other techniques used for GaN growth. The AMMONO crystals were of pure hexagonal phase and had a low electron concentration of about 5×10¹⁵ cm⁻³. Their luminescence was very intensive and homogenous. At helium temperatures exciton recombinations of record narrow lines (FWHM down to 1 meV) dominated the luminescence spectra. Energy positions of the exciton lines did not depend on excited microcrystals which confirmed they were strain-free.     

Photoacoustic Spectroscopy Investigation of Zinc Oxide/Diatom Frustules Hybrid Powders

Photoacoustic spectroscopy investigation was carried out on ZnO nanoparticles grown at 80 °C on porous surface of diatomite (DE) by sol–gel technique, using zinc acetate dihydrate as ceramic precursor and triethanolamine to mediate the surface growth of the nanoparticles. Absorption and scattering characteristics of hybrid ZnO/DE powder in the UV–Vis range were inferred by photoacoustic spectroscopy, and results were analyzed based on Helander’s theory. In particular, we discussed in detail the procedure to calculate the absorption and scattering spectra of the hybrid powder showing how from the scattering coefficient in the 300–450 nm range it is possible to obtain information on the size distribution of the ZnO nanospheres. By applying photoacoustic spectroscopy for different modulation frequencies, we showed that is also possible to perform a size distribution depth profile of the ZnO aggregates, opening the way to interesting developments in this research field.