Fine Structures of the Permittivity and Characteristic Losses of Electrons in Fluorite

Experimental-computational spectra of the permittivity and characteristic losses –Im^–1 for energies in the range 5–21 eV at a temperature of 4.2 K and theoretical spectra of and –Im^–1 of a fluorite crystal are resolved into elementary transition bands. The parameters of transition bands (energies of their maxima E _i, band halfwidths H _i and areas S _i, and oscillator forces f _i) are determined. A correlation of the spectral bands of and –Im^–1is established, and their specific features are elucidated.     

The photoexcitation and photoluminescence of the crystalline tetrahedral complexes of manganese(II) chloride with hydrochloride of phenazone and aminophenazone

Summary The excitation and emission spectra of the complexes (PH)₂MnCl₄ and (APH)₂. MnCl₄ have been studied. All the bands characteristic of excitation transitions ofd ⁵ configuration — the manganese(II) ion being of tetrahedral symmetry — were identified. The spectrum was interpreted in terms of the Orgel's weak field matrix for quartet levelsd ⁵; and the Racah's parametersB andC, the secular determinants, the ground terms and the field strength of thsse complexes were calculated. The 10Dq value for either of the two compounds was found to be 400 cm^–1.The theories of a harmonic oscillator make possible the determination of characteristic parameters from the emission spectrum.The character and the arrangement of bands of excitation and emission spectra — green luminescence — of the crystals are indicative of tetrahedral structure of the complexes. The phenomenon of luminescence has been explained by the⁴ T ₁(G) ⁶ A ₁(S) transition.     

VUV emission model of REB-heated plasma

VUV emission model of a hygrogen plasma with oxygen impurity (T _e=tens of eV,n _e 10¹⁴–10¹⁶ cm^–3,ⁿimp=1–3 % n_e) is constructed in order to judge different possibilities of plasma diagnostics (especiallyT _e measurements) in the REBEX experiments. Two sets of calculations based on the nonstationary corona model are performed: time dependent continuous and line spectra in the range 5 eV—5 keV in the constantT _e approximation (discussion ofT _e measurements by the filter-method) and time dependent intensities of selected spectral lines (2s-2p type) of ionsO ²⁺–O⁵⁺ at variableT _e (including plasma heating by REB and radiative cooling). A possibility of plasma energy content determination from radiation losses is shown.We would like to acknowledge many helpful discussions with dr. P. unka; we thank also dr. J. Ullschmied for comparing our results with diamagnetic measurements.     

Solubility of Na2Co3 in NaCl:CaCl2 crystals

Measurements of electrical conductivity of NaCl 10^–5 molar fr. CaCl2 (1–80)×10^–5 molar fr. Na₂CO₃ crystals have been used to determine the temperature dependence of the solubility of CO₃-ions over the temperature range from 75 to 530 °C. The total solubility of CO₃-ions and that of [CO ₃ ^2– -vacancy] complexes may be expressed by simple relationships andc _ka=3·19× 10^–2 exp (–0·25 eV/kT), resp. The heat of solution of complexes is equal to 0·25 eV and that of free CO ₃ ^2– ions is higher than 1·2 eV. Under conditions of the thermal equilibrium between the solid solution and precipitate, the ratio of Na₂CO₃ and CaCO₃ components in the precipitate has been calculated at various temperatures and CO₃ concentrations.     

Influence of the acoustic phonon scattering anisotropy on the distribution function and the electronic transport inn-Si

The excess noise of dc current-carrying thin metal wires in gases of different kind and pressure has been investigated. The noise depends on the kind of the gas. Therefore its origin must be in the gas or in the boundary between the metal and the gas. By means of a simple theory the power spectrumW _s of the random heat current _s flowing into the gas (surface source) can be calculated from the observed noise voltage. At frequencies above 100 HzW _s is given by a Nyquist formula, at lower frequencies an additional term 2 · 10^–3 · ₀ ² /N_hf is superimposed (₀ = dc heat current,f=frequency). The numberN _h characterizes this Hooge-contribution. A lot ofN _h -values for different metals, gases, pressures and heating currents have been measured.N _h is smaller for light gases and small wire diameters. For heavy gasesN _h is about ten times larger. A possible qualitative explanation is given. At higher pressures and heating currents thef ^–1 dependence turns over into af ^–3 one. This may be due to gas convection.Dedicated to Prof. Dr. H.E. Müser on the occasion of his 60th birthday     

Electron Energy Loss Spectra of the Organic Complexes of Europium

In the electron energy loss spectra (EELS) of the organic europium complexes Eu³⁺ (BTFA)₃TPPO and Eu³⁺(BrBTFA)₃TPPO in a gas phase obtained on excitation by monokinetic beams of electrons of different energies in the range 12–50 eV, we have identified the bands associated with the electron transitions S ₀–S ₁, S ₀–S ₂, and S ₀–S ₃. The connection of these transitions with the structural groups of the complexes is established. The addition of the bromine atom to the phenyl ring of diketonate leads to the rise in the relative intensity of the S ₀–S ₂ band. The singlettriplet transitions manifest themselves in the region 2.5–3.2 eV and contribute to the S ₀–S ₂ band of the electron energy loss spectra.     

Analyticity properties and a convergent expansion for the inverse correlation length of the low-temperatured-dimensional Ising model

We show that the inverse correlation lengthm(z) of the truncated spin-spin correlation function of theZ ^d Ising model with + or — boundary conditions admits the representationm(z) = –(4d–4)ln z(1–_d1) + r(z) for smallz=e ^–, i.e., large inverse temperatures is ad-dependent analytic function atz = 0, already known in closed form ford = 1 and 2; ford = 3 b_n can be computed explicitly from a finite number of the Z^d limits of z = 0 Taylor series coefficients of the finite lattice correlation function at a finite number of points ofZ ^d.     

Annealing behavior ot trap-centers in silicon containing A-swirl defects

The annealing behavior of trap-centers was studied in float-zone silicon wafers containing A-swirl defects. Samples from areas of high and low A-swirl density were annealed in nitrogen ambient between 100° and 900 °C, and analysed using the Deep Level Transient Spectroscopy. The results indicate, that two levels atE _c }-0.07 eV, _n=4.6×10^–16 cm², andE _c–0.49eV, _n=6.6×10^–16cm² are caused by one defect, for which the silicon di-selfinterstitial is a likely interpretation. A level atE _c }-0.11 eV was assigned to interstitial carbon. Both defects annealed out at about 170 °C. After 600 °C annealing an additional level atE _c–0.2 eV was detected, which was attributed to an interstitial silicon carbon complex. Heat treatment at 800 °C generated a new level atE _c–0.49 eV, _n=2.9×10^–16cm² only in the area of high A-swirl defect density. This level was also observed after oxidation and subsequent annealing of silicon.     

Influence of magnetic field on cesium thermionic energy converter

This article deals with the calculation of the influence of the magnetic field upon the electric current of a thermionic converter presupposing the approach to conditions in a low-pressure cesium converter. The distribution of the starting velocities of the emitted electrons is considered firstly as independent of the angle from the perpendicular to the emitter plane, and secondly according to the cosine law.The magnetic field effect from the converter current is calculated and compared with the calculations in the papers by Schock [1] and Block [2]; the effect of the external magnetic field is verified by measurements on a solar thermionic converter prototype.Symbols F=I/I ₀ factor of current reduction from magnetic field effect - ¯F value of factorF (when the magnetic field is not constant) - I [A/m²] density of collector current (real current influenced by magnetic field) - I ₀ [A/m²] theoretical density of collector current (in ideal case equals electron emission current) - T _e [°K] electron gas temperature; assumed equal to emitter temperatureT _E [°K] - B[Wb/m²] magnetic induction (field) - D[m] distance from emitter to collector - R[m] radius of electrodes, emitter and collector - r[m] variable radius in the limits 0 toR - V [m/s] random velocity of electron - v _xz [m/s] component of the vectorV inx-z plane - v _m =2kT _E /m most probable velocity in the velocity distribution according to Maxwell and Boltzmann - w-v _xz /v _m relatively expressed electron velocityv _xz - the angle of any vectorV - [m] radius of circular electron path - n [m^–3] number (density) of electrons with certain value of random velocity - n ₀ [m^–3] total electron number (density) - n ₁ [m^–3] number of electrons returned to emitter by means of magnetic field - N ₀ [m^–2s^–1] total flow of thermionic electrons emitted from a unit surface - N ₁ [m^–2s^–1] partial flow of electrons returned to emitter - P=N ₁/N₀ relatively expressed flow of electrons returned to emitter (whenB = const.) - ¯P mean value ofP (whenB const.) - F _cos, ,P _cos, values asF,¯F,P,¯P in case of velocity distribution according to cosine law - m=9·107×10^–31 [gk] electron mass - e=1·60×10^–19 [C] electron charge - k×1·38×10^–23 [J/grad] Boltzmann's constant - ₀ 1·257×10^–6 [H/Vs] permeability of vacuum     

On the mechanism of the induced anisotropy of magnesium ferrites in the range of higher temperatures

A simple mechanism explaining not only the magnitude but also the type of induced anisotropy on the magnesium ferrite Mg_0·78 Fe_2·22 O_4·026 in the temperature range from 400 to 500°K has been designed. The experimentally estimated values of the microscopic bond energyl _p 7×10^–16 erg of the configuration contributing to theF-type anisotropy and the activation energy _exp = 1·1 eV are in good correspondence with the valuesl _d1·6×10^–16erg and _cal = 1·1₅ eV which have been calculated theoretically.Dedicated to Professor Dr. Jaromír Bro on his sixtieth birthday.The author would like to express his thanks to Dr. S. Krupika for valuable discussions and his interest in this paper.     

Physical effects which distort measurement of the rest mass of the neutrino from beta spectra

Various physical effects which distort the result at the 1-eV accuracy level are discussed in connection with the experimental possibility of raising the sensitivity to the neutrino rest mass m _v ² to a value of the order of (1 eV)² in measurements of the beta spectra of tritium decay. There is no contradiction in an integrated spectrometer between the accuracy, the resolution, and the statistics, which there is in a differential spectrometer, and the mass sensitivity range is significantly greater. The statistical reliability of the measurements on section A of the Curie curve — Fig. 1 — is discussed, in which the problem reduces to the determination of the coefficients of the expansion (4). It is necessary in a monolayer source at an accuracy level of the order of 1–3 eV to introduce correctionfor the formation of an excited helium atom. The remaining effects are at the 1-eV level. The possibility of measuring the Curie curve in region C — near the cutoff — is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 29–36, April, 1984.     

The density of states at the fermi level of the non-crystalline semiconductors

Conclusion On the basis of our experimental results on glassy As₂Te₃ we have shown that the results on the films of As₂Te₃, concerning the conductivity _F (approximately linearly rising with the frequency) and the following density of states at the Fermi level are affected mainly by the thin film nature of samples.The estimated value of the density of statesG(E _F ) at the Fermi level for glassy As₂Te₃ isG(E _F ) 10¹⁸ eV^–1 cm^–3 which is no longer in contradiction with the other results.     

Beta-decay asymmetries in polarized12B and12N and theG-parity non-conservation

The decay asymmetries (A) in polarized¹²B and¹²N have been measured as a function of -ray energies (E). The coefficients _± inA = ±P(p/E) (1+_± E) have been determined to be _–(¹²B) =+(0.31±0.06)%/MeV and ₊(¹²N) = –(0.21±0.07)%/MeV. The experimental value, _––₊=(0.52±0.09)%/MeV, is larger than the prediction according to conservation of vector current which includes no second-class current, _––_{+ CVC}0.27%/MeV, and indicates the existence of the second-class induced-tensor current.This work has been done in collaboration with I. Tanihata and J. Göring.     

Influence of Oxygen Vacancies on the Luminescence Spectra of Y2O3 Thin Films

Luminescence spectra of Y₂O₃ thin films annealed in air and in vacuum are investigated. It is established that the presence of oxygen vacancies leads to a decrease in the intensity of the luminescence band with a maximum at 3.4 eV (related to emission of selflocalized Frenkel excitons describing the excited state of a molecular ion (YO₆)^9–) and of the luminescence band with a maximum at 2.9 eV (related to the anion sublattice). It is revealed that the oxygen vacancies also lead to a decrease in the luminescence intensity in the 2.60, 2.35, 2.10. 1.90, and 1.70 eV bands that are related to radiative recombination in the donor–acceptor Y³⁺–O^2– pairs. The donor–acceptor distances are calculated.     

Brightness waves and brightness-current curves in alkali halide electroluminescence

A kinetic model has been formulated for electroluminescence (EL) in alkali halide crystals (AHC) on the basis of existing measurements and theoretical concepts on prebreakdown electroluminescence. An expression is derived for the intensity, which contains parameters S₁, S₂, and S₃, which are the probabilities of excitation, ionization, and stepwise ionization for the emission centers when an electron passes through section . If the current density is not more than 1 A/cm², the EL brightness waveform reproduces the exciting current pulse within the excited-state lifetime, with the amplitude directly proportional to the current density. As the current density increases, the wave becomes damped, because the ionized emission centers are excluded from the EL. The observed waves for KBr have been examined for current densities up to 1 A/cm² and agree with the theoretical ones. A method is proposed for determining S_x as a function of emission-center concentration from the initial parts of the brightness-current curves.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 82–86, April, 1988.     

On the scalar-tetradic theories of gravitation: Cosmology and gravitational radiation

The so-called scalar-tetradic theoriesA andB generalize Møller's theory of gravitation. In this work, some results previously obtained in Møller's theory are extended to the theoriesA andB. When the parametersW and ^*. of the theoryA are not too small (or large), the losses of energy and angular momentum of a nongravitationally bound system are proved to be the same as in general relativity. The basic equations of cosmology are derived and some topics are treated. In particular, any density of energy ₀ (10^–29 g cm^–3 ₀ 10^–31 g cm^–3) appears to be compatible with the observational values ofH ₀ (Hubble constant) andqo (deceleration parameter) in the theory A; thus, no intergalactic energy assumption is necessary.     

Spin-dependent photoabsorption at theL-edges of ferromagnetic Gd and Tb metal

The spin-dependent absorption of circularly polarized x-rays is studied at theL-edges of ferromagnetic Gd and Tb metal. At theL ₁-edge a spin-dependent part of the absorption coefficient of 10^–3–10^–2 is observed. Strong resonance absorption known as white line occurs at theL ₂- andL ₃-absorption onset. Correlated with it one finds large spin-dependent absorption effects with amplitudes of a few percent. The spin-dependent absorption spectra reflect the profiles of the spin densities of the states populated in the absorption process. Thep-states show spin densities correlated with the first two flat bands above the Fermi level. The spin density of thed-like states is concentrated in the energy range of the white line. In Gd a splitting of (0.5–0.6) eV of the unoccupied 5d spin up and spin down bands is indicated for both spin-orbit partners. In Tb a large dependence of the 5d spin density on the spin-orbit configuration is observed. The experimental results on the spin densities in Gd are compared with band structure calculations for the ferromagnetic ground-state. The theoretical and experimental spin density profiles agree well for thep-states but not for thed-states. The discrepancy concerning thed-states may be attributed to core-hole polarization effects in the absorption process.     

Frequency Dependence of the Components of Dielectric Permeability and Characteristic Losses of Fluorite

The ₁(E), –Im^–1, and Re^–1 spectra of the fluorite crystal are calculated on the basis of the experimental (10–35 eV) and theoretical spectra ₂(E) (10–27 and 8–20 eV). They were employed to decompose the ₂(E) and –Im^–1 spectra into elementary components. The most intense transverse and longitudinal components of transitions and their parameters have been determined. The correlation between two types of components of transitions and their distinguishing features have been established.     

Low temperature acoustic properties in YBa2Cu3O7−δ

Temperature dependencies of acoustic lossesQ ^–1 and of relative sound velocity change v/v in YBa₂Cu₃O_7– up to 60 K are calculated by the tunneling model theory. The tunneling systems are related to the off-centered positions of the apical oxygen atoms O(A) and are described through the pseudo-Jahn-Teller effect. Tunneling systems' parameters are distributed in narrow range of values and are in correspondence with the experimentally observed infrared phonon spectra and thermal ellipsoids of O(A). Respective relaxation times are calculated by the adapted reaction rate method. The calculatedQ ^–1(T) and v(T)/v dependencies are in good agreement with the experimental data, which is an additional support to the conclusion about the existence of tunneling systems in YBa₂Cu₃O_7– due to the pseudo Jahn-Teller effect.