Hypersonic properties of undoped and Cr-doped bismuth germanium oxide

The velocity and attenuation of hypersonic waves propagating along the [100] or [110] axis of undoped and Cr-doped Bi₁₂GeO₂₀ have been measured at frequencies from 0.76 to 1.65 GHz and at temperatures of 4.5, 24, 77 and 293 K. The second-order elastic constants and Debye temperature have been calculated from these results. The measurements and the results of the calculations are used to interpret the attenuation in terms of collisions between low-energy phonons, constituting the sound wave, and thermal phonons. The thermal-phonon lifetime and Grüneisen constant have been estimated for undoped and doped material.     

Spatial resolution of an incoherent-to-coherent converter using bismuth germanium oxide

An incoherent-to-coherent converter is constructed with a bismuth germanium oxide crystal. Several experiments are carried out with emphasis on the spatial resolution. It is found that the line width of the read-out image is approximately proportional to the logarithm of the write-in pulse duration, and that longer exposures cause the read-out image to deteriorate sooner. Several ways to increase the spatial resolution of the converter are discussed.     

锗酸铋阵列探测器用于中子激发发射计算机断层扫描成像

 中子激发发射计算机断层扫描成像对探测器有着较高的要求,为了探讨利用传统阵列探测器实现其应用的可行性,利用模拟的方法给出了锗酸铋（BGO）晶体阵列探测器的基本性能。对高能光子在单根BGO晶体中的能谱进行了分析,提出叠加相邻晶体信号以提高能量分辨率的修正方法。结果表明:此方法能够很大程度上优化输出能谱,并能够得到较好的空间分辨率。     

锗酸铋阵列探测器用于中子激发发射计算机断层扫描成像

中子激发发射计算机断层扫描成像对探测器有着较高的要求,为了探讨利用传统阵列探测器实现其应用的可行性,利用模拟的方法给出了锗酸铋（BGO）晶体阵列探测器的基本性能。对高能光子在单根BGO晶体中的能谱进行了分析,提出叠加相邻晶体信号以提高能量分辨率的修正方法。结果表明:此方法能够很大程度上优化输出能谱,并能够得到较好的空间分辨率。     

Electromechanical properties of bismuth germanium oxide (Bi12GeO20)

The elastic and piezoelectric constants and their temperature coefficients of bismuth germanium oxide have been determined. All of the elastic and piezoelectric constants were obtained from dynamic measurements of piezoelectrically driven narrow bars and thin plates at the temperature 22 °C. The temperature coefficients were measured on the same resonators in the temperature range from 16 °C to 70 °C. The thermal expansion measured in the temperature range from 50 °C to 200 °C is also given.The author wishes to acknowledge the help rendered by Professor Ing. Dr.Jaroslav Stank in connection with the measurement of the thermal expansion coefficient and by R.Trepera in the course of the preparation of the measured resonators.     

Superbroadband 1310 nm emission from bismuth and tantalum codoped germanium oxide glasses

Near-infrared broadband emission from bismuth-tantalum-codoped germanium oxide glasses was observed at room temperature when the glasses were pumped by an 808 nm laser diode. The emission band covered the O, E, S, C, and L bands (1260-1625 nm), with a maximum peak at approximately 1310 nm, a FWHM broader than 400 nm, and a lifetime longer than 200 micros. The observed broadband luminescence was attributed to bismuth clusters in the glasses. Bismuth-tantalum-codoped germanium oxide glass might be promising as amplification media for broadly tunable lasers and wideband amplifiers in optical communications.     

Inelastic alpha-scattering from the stable even germanium isotopes

Scattering of 31.5 MeV α-particles from the stable even Ge isotopes has been studied with an energy resolution of 15–20 keV FWHM. Angular distributions were measured for excitation energies of up to 5.2 MeV. Most of the levels are well described by collective DWBA calculations with vibrational model form factors. An implicit folding procedure was used to derive isoscalar transition rates. The distribution of the isoscalar multipole strength reveals an increasing fragmentation with increasing neutron number. A detailed comparison with the spectroscopic results of a recent (p, p′) study is made.     

Dielectric behaviour of ketone-amine binary mixtures at microwave frequencies

Values of dielectric constant (ε′) and loss factor (ε″) have been experimentally determined for binary liquid mixtures of ethyl methyl ketone+ethylenediamine and methyl isobutyl ketone+ethylenediamine at 9.44 GHz microwave frequencies at 30°C. The values ofε′ andε″ have been used to evaluate the molar polarization, apparent polarization and the excess permittivities. Excess refractive index, viscosity and activation energy of viscous flow have also been estimated. These parameters have been used to explain the formation of 1:1 complexes for both the systems.     

Solitons generated by self-organization in bismuth germanium oxide single crystals during the interaction with laser beam

We present here the experimental, theoretical, and numerical investigations of Kerr solitons generated by self-organization in black and yellow high quality bismuth germanium oxide (Bi₁₂GeO₂₀) single crystals. A picosecond laser beam of increasing power induces competing cubic and quintic nonlinearities. The numerical evolution of two-dimensional complex cubic-quintic nonlinear Schrödinger equation with measured values of nonlinearities shows the compensation of diffraction by competing cubic and quintic nonlinearities of opposite sign, i.e., the self-generation and stable propagation of solitons. Experiments as well as numerical simulations show higher nonlinearity in the black Bi₁₂GeO₂₀ than in the more transparent yellow one.     

Inelastic scattering of tritium-source antineutrinos on electrons of germanium atoms

Processes of the inelastic magnetic and weak scattering of tritium-beta-source antineutrinos on the bound electrons of a germanium atom are considered. The results obtained by calculating the spectra and cross sections are presented for the energy-transfer range between 10 eV and 18 keV.     

Thin oxide films on germanium

The optical constants, i.e. the refractive index and thickness, were determined for thin oxide films which were produced by heating single-crystal samples of germanium to temperatures ranging from 450° C to 600° C. The ellipsometric method was used to determine the thicknesses and the refractive indices of the films. The paper is dedicated to the memory of Dr. A. Vaíek, Professor of the J. E. Purkyn University in Brno, who died on Nevember 16, 1966.     

Splitting of frequencies of optical phonons in tensile-strained germanium layers

Tensile-strained germanium films in Ge/GeSn/Si/GeSnSi multilayer heterostructures grown by molecularbeam epitaxy on Si(001) substrates are investigated by Raman spectroscopy. Biaxial tensile strains in the films reach 1.5%, which exceeds values previously obtained for this system. Splitting of frequencies of long-wavelength optical phonons is experimentally observed; i.e., the shift of the frequency of the singlet induced by biaxial tensile strains is larger than the shift of the frequency of the doublet in agreement with calculations. The strain-induced shift of Raman scattering peaks from two-phonon scattering in germanium is also detected.     

Elastic constants of the SrLaAlO4 and SrLrGagaO4 crystals measured at ultrasonic and hypersonic oustic frequencies

Elastic constants measured by Brillouin light-scattering experiments were compared with results estimated from the pulse-echo-overlap method for the ultrasonic frequency to find dispersion in their values. In this way Brillouin hypersonic experiments complete the ultrasonic results. The present investigation includes a careful analysis of the accuracy of the results. The measured values of elastic constants suggest a weak dispersion in acoustic wave velocities. However, given the magnitude of the experimental errors, it is difficult to conclude about the dispersion.     

Inelastic scattering of slow electrons by lanthanum oxide

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 6, pp. 988–993, December, 1991.     

磷、铋掺杂半导体锗光学性质的第一性原理研究

采用基于密度泛函理论框架下的第一性原理计算,研究了不同浓度N型掺杂锗的电子结构和光学性质.掺杂元素分别为磷和铋,并对掺杂后的电子态密度和光学性质进行计算、分析.计算结果表明:N型掺杂会使得费米能级向导带方向移动.在低能区段,介电函数、折射率和吸收系数都受到影响,但到高能区后只有消光系数和吸收系数会被影响;反射率在整个能区都受影响,在中能区掺杂会使反射率提高,在低、高能区会减弱反射率;对损失函数的影响是掺杂浓度越高、损耗峰越小、峰值出现处能量越高.研究结果对N型掺杂半导体锗的光学应用具有一定的指导意义,可以根据上述结论有针对性地调节掺杂浓度和能量范围.     

Velocity of water diffusion through germanium oxide

The diffusion of water through an oxide film on germanium was investigated by measurement of the surface conductivity, and a relation was found between the coefficient of diffusion and the humidity of the ambient medium.     

Inelastic diffraction at collider energy

s-channel unitarity strongly constrains the amount of inelastic diffraction at collider energy, and allows to predict its dependence on the impact parameter and to compute useful upper bounds at even higher energies.     

Inelastic scattering at high energy

A derivation by Byron of the Glauber wavefunction for inelastic scattering without the explicit introduction of the nonmoving bound particle assumption is shown in fact to have this restriction implicitly.