Proton mobility in HxWO3 measured by proton magnetic resonance

An NMR study for a powder sample of H_xWO₃ prepared by the reduction of WO₃ with zinc grains and a dilute HCl is reported and the temperature dependence of the correlation time and the proton mobility estimated from the linewidth of proton magnetic resonance (PMR) is presented. The correlation time can be described by a single exponential line $\text{τ = τ}{}_0\text{exp}\text{(}\text{E}\text{kT}\text{)}$, where τ₀ = 1.1 × 10^-10 sec and E = 0.13 eV. The proton mobility is compared with the one obtained for an amorphous film by bleaching current measurement.     

Relaxation phenomena in TlGa<Subscript>0.99</Subscript>Fe<Subscript>0.01</Subscript>Se<Subscript>2</Subscript> single crystals

The relaxation electronic phenomena occurring in TlGa_0.99Fe_0.01Se₂ single crystals in an external dc electric field are investigated. It is established that these phenomena are caused by electric charges accumulated in the single crystals. The charge relaxation at different electric field strengths and temperatures, the hysteresis of the current-voltage characteristic, and the electric charge accumulated in the TlGa_0.99Fe_0.01Se₂ single crystals are consistent with the relay-race mechanism of transfer of a charge generated at deep-lying energy levels in the band gap due to the injection of charge carriers from the electric contact into the crystal. The parameters characterizing the electronic phenomena observed in the TlGa_0.99Fe_0.01Se₂ single crystals are determined to be as follows: the effective mobility of charge carriers transferred by deep-lying centers μ_f=5.6×10^?2 cm²/(V s) at 300 K and the activation energy of charge transfer ΔE=0.54 eV, the contact capacitance of the sample C _c =5×10^?8 F, the localization length of charge carriers in the crystal d _c =1.17×10^?6 cm, the electric charge time constant of the contact τ=15 s, the time a charge carrier takes to travel through the sample t _t =1.8×10^?3 s, and the activation energy of traps responsible for charge relaxation ΔE _σ = ΔE _Q = 0.58 eV.     

Proton spin relaxation in hexagonal ice

Measurements of the rotating frame proton spin relaxation timeT _1p in hexagonal ice single crystals as a function of temperature ? for various rotating magnetic field strengths reveal the expectedT _1p minimum at the lowest practicable field values. This allows a very precise determination of the proton correlation (? molecular jump) time τ_c and the related activation energy ΔE by means of the theoretical reasoning of relaxation spectroscopy. We find the Arrhenius-law temperature dependenceτ _c=1.99×10^?17exp(0.603/8.61×10^?5 ?)sec, which is in good agreement with our earlier indirect derivation.     

Messung der Verweilzeit von He-Atomen an Glasoberflächen

Mean sticking times of helium on a glass surface are determined at very low pressures from nonstationary molecular flow through glass capillaries. The temperature range covered is 13.8 °K to 20.4 °K. Resulting sticking times are of the order of 10^?7 to 10^?5 sec. They show a characteristic dependence on temperature and pressure. These measurements can be interpreted by means of a simple model: He-atoms mostly are bound to the surface with an adsorption energyE of 229 cal/mol?0.01 eV (±20%). However with a probability of 10^?4 the energy is 530 cal/mol?0.023 eV (±6%). In both cases sticking times τ follow the equation τ=τ₀exp(E/RT) where τ₀ is about 10^?9 to 10^?10 sec.     

CeAlO<Subscript>3</Subscript> crystals: Preparation and study of their electrical and optical characteristics

Crystals of cerium aluminate with perovskite structure were obtained using the cold-crucible technique. The electrical and optical properties of cerium aluminate were studied in air in the range 300–1300 K. The main characteristics of CeAlO₃ at T=300 K are a follows: electrical conductivity σ=10^?7 S/cm, dielectric permittivity ?=3000–10000 (both measured at a frequency of 1000 Hz), thermal band-gap width ΔE=2.3±0.5 eV, and optical width δE=2.65±0.25 eV, which decreases at a rate of ?0.62×10^?3 eV/K with increasing temperature in the 300-to 1500-K interval.     

The density and pressure of helium in bubbles in metals

Abstract

The energy shift of the He 1¹S₀?2¹P₁ transition, ΔE(n), can be used to determine the density, n, of He in bubbles in metals. A self-consistent band structure calculation for solid fcc He yields a linear relationship ΔE=C.n with C _th=22 × 10^?3 eV nm³. Systematic electron energy loss spectroscopy and transmission electron microscopy studies of He bubbles in Al for various He doses and temperatures result in C_exp=(24±8).10^?3 eV nm³ in agreement with theory. The analysis is consistent with the assumption that dislocation loop punching is the dominant bubble growth mechanism during high-dose room temperature implantation. The application to He bubbles in Ni indicates a maximum He density of n=0.2 × 10³ nm^?3 for which He should be solid at room temperature.     

First direct observation of strong interaction spin-orbit effects in antiprotonic atoms

The strong ¯p-nucleus spin-orbit interaction was investigated in a measurement of the strong-interaction effects of the 9→8 transition in ¯p ¹⁷⁴Yb at the Low-Energy Antiproton Ring (LEAR) at CERN. This measurement was part of an experimental programme where, for the first time, the fine-structure components of the last observable X-ray transition in a ¯p atom, which carries information on the strong ¯p-nucleus interaction, were resolved and studied individually. The observed splitting ΔE _exp=2408±26 eV consists of the electromagnetic fine-structure splitting ΔE _FS=2350 eV and an additional splitting Δ?=58±26 eV. In addition, one finds a significant difference in the level widths of Δ=195±59 eV with the larger value_?=1216±41 eV for the lower fine-structure level. This experiment follows an earlier measurement on ¯p ¹³⁸Ba, where the transition 8→7 is influenced by the strong interaction. In this case, however, the fine-structure components could not be resolved. The results for¹⁷⁴Yb may be attributed to a spin-orbit (LS) term in the complex strong-interaction potential.     

Properties of single vacancies and of divacancies in copper

The electrical resistivity change at high temperatures due to vacancies was determined as a function of temperature. From the data E^F_1V=1.00 eV, E^B_2V=0.45 eV and about C^tot_V=4 × 10^-4 at the melting point results.     

Structure-mediated transition in the behavior of elastic and inelastic properties of beach tree bio-carbon

Microstructural characteristics and amplitude dependences of the Young modulus E and of internal friction (logarithmic decrement δ) of bio-carbon matrices prepared from beech tree wood at different carbonization temperatures T _carb ranging from 600 to 1600°C have been studied. The dependences E(T _carb) and δ(T _carb) thus obtained revealed two linear regions of increase of the Young modulus and of decrease of the decrement with increasing carbonization temperature, namely, ΔE ～ AΔT _carb and Δδ ～ BΔT _carb, with A ≈ 13.4 MPa/K and B ≈ ?2.2 × 10^?6 K^?1 for T _carb < 1000°C and A ≈ 2.5 MPa/K and B ≈ ?3.0 × 10^?7 K^?1 for T _carb > 1000°C. The transition observed in the behavior of E(T _carb) and δ(T _carb) at T _carb = 900–1000°C can be assigned to a change of sample microstructure, more specifically, a change in the ratio of the fractions of the amorphous matrix and of the nanocrystalline phase. For T _carb < 1000°C, the elastic properties are governed primarily by the amorphous matrix, whereas for T _carb > 1000°C the nanocrystalline phase plays the dominant part. The structurally induced transition in the behavior of the elastic and microplastic characteristics at a temperature close to 1000°C correlates with the variation of the physical properties, such as electrical conductivity, thermal conductivity, and thermopower, reported in the literature.     

Carbon segregation on a tungsten surface

New measurements are performed and a comprehensive analysis of experimental data is made on the dependence of equilibrium carbon coverage θ on a tungsten surface on its temperature and the degree of carbon loading. It is shown that if the volume is free of carbon, the variation of θ for T≥1400 K can be approximately described by the balance between the carbon flows through the boundary with the activation energy for transition into the bulk E₁=4.6 eV and the segregation energy ΔE=1.7 eV. For tungsten loaded preliminarily with carbon to a content of ≈10^?2 at. %, the θ(T) relation cannot be described in terms of the equilibrium conditions with constant E₁ and ΔE, because these quantities depend on the degree of carbon loading; E₁ grows from 4.6 to 6.8 eV and ΔE grows from 1.7 to 2.3 eV with an increase in carbon content from 0 to 10^?2 at. %. These variations are attributed to the bonds becoming stronger in carbon-loaded tungsten with increasing carbon content.     

Trapping probabilities and desorption energies of alkali atoms on a clean and an oxygen covered tungsten (110) surface

Alkali atoms were scattered with hyperthermal energies from a clean and an oxygen covered (θ ≈ 0.5 ML) W(110) surface. The trapping probability of K and Na atoms on oxygen covered W(110) has been measured as a function of incoming energy (0–30 eV) and incident angle. A considerable enhancement of trapping on the oxygen covered surface compared to a clean surface was observed. At energies above 25 eV there are still K and Na atoms being trapped by the oxygen covered surface. From the temperature dependence of the mean residence time τ of the initially trapped atoms the pre-exponential factor τ₀ and the desorption energy Q were derived using the relation: $\text{τ = τ}{}_0\text{exp}\text{(}\text{Q}\text{kT}{}_{\mathrm{<mtext>s</mtext>}}\text{)}$. On clean W(110) we obtained for Li: $\text{τ}{}_0\text{= (8 ±}\text{8}\text{4}\text{) × 10}{}^{\mathrm{?14}}\text{sec}$, Q = (2.78 ± 0.09) eV; for Na: τ₀ = (9 ± 3) × 10^?14 sec, Q = (2.55 ± 0.04) eV; and for K: τ₀ = (4 ± 1) × 10^?13 sec, Q = (2.05 ± 0.02) eV. Oxygen covered W(110) gave for Na: τ₀ = (7 ±3) × 10^?15 sec, Q = (2.88 ± 0.05) eV; and for K: $\text{τ}{}_0\text{= (1.3 ±}\text{0.9}\text{0.6}\text{) × 10}{}^{\mathrm{?14}}\text{sec}$, Q = (2.48 ±0.05) eV. The adsorption on clean W(110) has the features of a supermobile two-dimentional gas; on the oxygen covered W(110) adsorbed atoms have the partition function of a one-dimen-sional gas. The binding of the adatoms to the surface has a highly ionic character in the systems of the present experiment. An estimate is given for the screening length of the non-perfect conductor W(110):k_s^?1≈ 0.5 Å.     

On EAS spectrum with extremely low content of hadrons in the primary-energy range ∼10<Superscript>14</Superscript>−10<Superscript>15</Superscript> eV

The distribution of energy fluxes of the hadron component of extensive air showers through an ion-ization calorimeter in the primary-energy range ～3 × 10¹³?10¹⁶ eV is considered. Extensive air showers with zero and minimum energy fluxes of the hadron component are selected. It is concluded that the primary-energy range E ₀ ≈ 1 × 10¹⁴?2 × 10¹⁵ eV contains isotropic γ radiation with a spectrum close to bell-shaped, having a maximum near E ₀ ≈ 2.2 × 10¹⁴ eV and an additional peak near E ₀ ≈ 1.6 × 10¹⁵ eV.     

Deep levels in gallium arsenide by capacitance methods

The three capacitance methods, i.e., TSCAP, PHCAP, and transient capacitance measurements, are applied to determine electronic properties of deep levels inn-GaAs. In the boat-grown wafer detected are the 0.30 eV electron trap withN _T =3.6×10¹⁶ cm^?3 andS _n =2.4×10^?15 cm², and the 0.75 eV electron trap withN _T =2.0×10¹⁶ cm^?3 andS _n =1.2×10^?14 cm². In the epitaxial wafer, the 0.45 eV hole trap is detected withN _T >1.5×10¹³ cm^?3 andS _p =1.4×10^?14 cm² as well as the 0.75 eV electron trap withN _T =2.4×10¹³ cm^?3.     

Specific features of the optical and electrical properties of polycrystalline CdTe films grown by the thermal evaporation method

The results of studying the physical properties of thin CdTe films obtained by the thermal evaporation method have been presented. The optical constants and the band gap of the films under study have been determined (E _g = 1.46 eV). It has been established based on the investigation of optical properties and the Raman spectrum of the films that they possess high structural quality. The activation energy of the electrical conductivity of CdTe films has been determined: E _a = 0.039 eV. The measured spectral dependences of the impedance of CdTe thin films are characteristic of the inhomogeneous medium with two time constants: τ_gb = R _gb C _gb = 1/ω_gb = 1.62 × 10^?3 s and τ_g = R _g C _g = 1/ω_g = 9.1 × 10^?7 s for grain boundaries and grains, respectively.     

Some nuclear and atomic properties of201Hg determined by conversion electron spectroscopy

Conversion electron measurements with an electrostatic spectrometer proved the existence of the 1,565±6 eV transition in²⁰¹Hg. The conversion intensity ratios,N ₁/N ₂ =1.2±0.2,N ₁/N ₃=1.1±0.2,N ₂/N ₃=0.92±0.15,N ₄/N ₃=0.03± 0.02 andN ₅/N ₃=0.04 ±0.02 were determined. These values agree with our calculations for the M1±E2 multipolarity with theE2/M1 mixing ratioδ ²=(l.l±0.3)xl0^?4 and exclude all pure multipolarities withL≦4. The total conversion coefficient for the aboveM1 +E2 mixture was evaluated to be (4.7±0.7)× 10⁴. The reducedB(M1, 1/2→3/2) probability was derived to be (3.9 ±1.2) × 10^?3 (e?/2Mc)². The natural widths of theN-subshell conversion lines in mercury were found to beΓ(N ₁)=8.3± 1.5,Γ(N ₂) =5.8±1.5 and Γ(N ₃) =6.5±1.0 eV. Monte Carlo calculations of electron scattering in matter yielded the conversion line shapes in qualitative agreement with the experiment.     

Multistage radiation-stimulated changes in the microhardness of silicon single crystals exposed to low-intensity β irradiation

Radiation-stimulated and postradiation changes in the microhardness of silicon single crystals exposed to irradiation with a low-intensity flux of β particles (I = 9 × 10⁵ cm^?2 s^?1, W = 0.20 + 0.93 MeV) are studied. It is established that the inversion of the radiation-induced plastic effect occurs at a characteristic irradiation time τ_c = 75 min; i.e., irradiation of silicon single crystals for a time τ < τ_c leads to nonmonotonic reversible hardening, whereas nonmonotonic reversible softening is observed under irradiation for a time τ > τ_c. It is demonstrated that there exists a correlation between the nonmonotonic dependences of the microhardness and the concentration of electrically active defects at acceptor levels with energies E _c ? 0.11 eV, E _c ? 0.13 eV, and E _c ? 0.18 eV on the irradiation time.     

Heavy fermion contributions to the anomalous magnetic dipole and quadrupole moments of theW-boson

The contribution of a massivet-quark to the anomalous magnetic moment (Δκ) and the quadrupole moment (ΔQ) of theW-boson is calculated. An upper bound of Δκ=1.5×10^?2 and ΔQ=2.5×10^?3 for the standard model is obtained. Additional contributions from extraE ₆ fermions is also discussed.     

Dipole reorientation from bound-polaron hopping in single crystal NiO

We report observation of a first order thermal depolarization peak at 190 K in NiO single crystals which we attribute to the reorientation of Ni³⁺Ni_V²⁺ dipoles. Analysis of the data in terms of these bound polarons, using a non-adiabatic hopping model, yields values of activation energy, E = 0.31eV and the polaron band width, J = 8.6 × 10^?6 eV.     

Camel's back induced stabilization of electron-hole liquids : GaP

A camel's back-like nonparabolicity of the longitudinal electron mass enhances the density of states and strongly stabilized an electron-hole-liquid. In GaP therefore the EHL density is doubled to 8.6 × 18¹⁸cm^?3 and the Fermi energy ratio E_F^h/E_F^e changes from 1.9 to 4.9. The theoretical binding energy agrees with the experimental E_B=17.5±3meV interpreting the luminescence at 2.30 eV as a superposition of liquid and plasma recombination radiation.     

Characterization and electrical behavior of new lithium chalcoborate thin films

Thin films obtained with glasses of the B₂S₃Li₂S and B₂S₃Li₂SLiI systems, using a vacuum evaporation technique have been investigated. In each system, amorphous thin films and starting glasses have the same composition and similar conductivities, about 10^?4 and 10^?3Ω^?1cm^?1 respectively at 25°C. The deposition rate was in both cases 140 Å s^?1. However, a thermal treatment at 90°C of the thin films containing lithium iodide enhances the conductivity by a factor of 10 and leads to lower activation energy (0.18 eV). This behavior has been identified as a Phipps effect and can be attributed to a quick ion diffusion along thin film - substrate interface. This interfacial region was found to show unique conduction properties including a very low Li⁺ migration enthalpy.