Structure of Electron Transitions of Corundum

The integral spectra of the dielectric permeability of corundum within the region 8–40 eV in the polarizations E C and E C are decomposed into 18 Lorentz elementary oscillators. Their principal parameters, namely, the energy E _i , halfwidth H _i , band area S _i , and height of the maximum _2max, are calculated and the main features are established. An analysis of the wellknown results obtained by two models of the reproduction of the ₂ spectra with the aid of a large number of fitting parameters and theoretical calculations of the corundum bands is carried out.     

Fast quasi-optical phase shifter based on the effect of induced photo conductivity in silicon

We study, both numerically and experimentally, a microwave commutator (phase shifter), whose active element comprises a metal plane mirror with a semiconductor plate on it. Phase shifting of the reflected microwave beam is attained by creating a conducting layer in the semiconductor by a laser with quantum energy approximately equal to the forbidden band width. Using a disk of high-purity silicon and a titatnium-sapphire pulsed laser, we study experimentally a 180° phase shifter operated with a Gaussian wave beam at a frequency of 30 GHz. Efficient phase shifting of the wave beam over a time of several nanoseconds is shown at a low power level.     

双流化床煤气化试验研究

建立了一套3米高的双流化床煤气化试验装置,煤在鼓泡流化床中热解气化,生成的半焦送入循环流化床中燃烧,两床间采用气动控制阀连接.分别采用神华烟煤、龙口褐煤和大同烟煤进行了试验.煤中的碳转化成煤气和烟气的总转化率达到90%以上;冷煤气效率随着窄气/煤比的提高而增加;采用神华煤时焦油产率可达到1.5%;采用龙口褐煤时气化效果较好,在气化炉空气/煤比为0.3 kg/kg时,冷煤气热值为10.7 MJ/Nm3,冷煤气效率为48%.经过分析计算,龙口褐煤产生煤气中的可燃成分主要来自热解.     

Spectra of characteristic losses and the electronic structure of sodium nitrite

The complete sets of optical functions for a NaNO₂ crystal are calculated in the energy range of 4 to 24 eV using the integral Kramers-Kronig relations, experimental reflectivity spectra, and theoretical spectra of permittivity. The main distinguishing features and patterns of optical properties are determined as functions of the direction of the light polarization vector. An analysis of the participation of electrons in the formation of optical spectra is presented.     

Structure of the local environment and hyperfine interactions of <Superscript>57</Superscript>Fe probe atoms in DyNiO<Subscript>3</Subscript> nickelate

The local structure of DyNiO₃ nickelate at both sides of the insulator (T < T _im) ? metal (T > T _im) phase transition was studied by probe ⁵⁷Fe Mössbauer spectroscopy. The character of change in the hyperfine parameters of probe iron atoms specifically near the phase-transition temperature (T ≈ T _im) was analyzed.     

Ultra-sensitive magnetometry based on free precession of nuclear spins

We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized ³He or ¹²⁹Xe samples with a SQUID as magnetic flux detector. The device will be employed to control fluctuating magnetic fields and gradients in a new experiment searching for a permanent electric dipole moment of the neutron. Furthermore, with the detection of the free precession of co-located ³He/¹²⁹Xe nuclear spins it can be used as ultra-sensitive probe for non-magnetic spin interactions, since the magnetic dipole interaction (Zeeman-term) drops out. Characteristic spin precession times T₂ ^* of up to 60 h were measured. The achieved signal-to-noise ratio of more than 5000:1 leads to an expected sensitivity level (Cramer-Rao lower bound) of δB≈1 fT after an integration time of 220 s and of δB≈10^-4 fT after one day. By means of a co-located ³He/¹²⁹Xe magnetometer, noise sources inherent in the magnetometer could be investigated, showing that CRLB is fulfilled, at least down to δB≈10^-2 fT. The reason for such a high sensitivity is that free precessing ³He (¹²⁹Xe) nuclear spins are almost completely decoupled from the environment. Therefore, this type of magnetometer is particularly attractive for precision field measurements where long-term stability is required.     

热交换器中氦气流量对生长蓝宝石温场影响的研究

采用热交换法生长蓝宝石晶体,通过数值模拟与实验研究了晶体生长过程中热交换器中氦气流量对温场的影响.结果表明:晶体生长过程中固液界面为近弧面;随氦气流量增大,晶体与熔体的温度下降,温度梯度增大;加热器功率缓慢上升.     

Crystal growth and defect crystal structure of CdF2 and nonstoichiometric phases Cd1 − x R x F2 + x (R = rare earth element or in). 5. Crystal structure of as-grown Cd0.9R0.1F2.1 (R = La-Nd) single crystals: Nanoclusters of structural defects

As-grown Cd_0.9 R _0.1F_2.1 (R = La-Nd) crystals were assigned to the CaF₂ structure type and their structure was determined by X-ray diffraction. A new octacubic cluster of structural defects in Cd_0.9 R _0.1F_2.1 phases is proposed. The changes in the anionic motif of the Cd_0.9 R _0.1F_2.1 phase can be explained as a result of the formation of tetrahedral [Cd_{4 ? n} R _n F₂₆] and inverse octacubic [Cd_{14 ? n} R _n F₆₈] clusters with, respectively, tetrahedral and cuboctahedral anionic groups as cores. It is established that fluctuations of the La concentration in the cross section of a Cd_0.9La_0.1F_2.1 crystal boule do not exceed 2.7%.