Mesure de la conductivite electrique totale du protoxyde de cobalt en fonction de sa composition definie par des electrodes d'alliage cobalt-platine,entre 1000 et 1400 K

The total electrical conductivity of cobaltous oxide has been measured from 1000 to 1400 K as a function of its composition, especially in the range of low oxygen pressures up to the limit of equilibrium with cobalt. These measurements have been carried out with monocrystalline samples of oxide placed between cobalt-platinum alloy electrodes; oxide composition is fixed by the activity of cobalt in the alloy which is also the activity of cobalt in oxide. Results are given by isotherm curves of the logarithm of conductivity versus the logarithm of oxygen pressure. The slope of these isotherms shows a regular variation between $\text{1}\text{4}$ and less than $\text{1}\text{6}$; this fact can only be explained by the successive effects of the formation of vacancies V″_Co, V′_Co and of intrinsic conductivity by electrons and free holes.     

Exchange energy for conduction electrons in (ZnMn)Se derived from spin-flip Raman scattering and magnetization

Spin-flip Raman scattering, magnetization, and susceptibility data for Zn_0.97Mn_0.03Se are reported. The exchange energy N_oα = 243 ± 10 meV for the conduction electrons is obtained from an analysis of the Raman and magnetization data. At large magnetic fields (H > 60 kOe), the spin-flip energy ΔE saturates at 14 meV. At low fields ΔE does not extrapolate to zero as H → 0, which is characteristic of scattering from donor-bound electrons. The low temperature magnetization curves are fit to a modified Brillouin function. The fit gives $\text{x}\text{?}\text{/x}\text{= 0.67}$ as the fraction of active magnetic ions, and an effective temperature T_eff = T + T_o with T_o = 1.1 K. The magnetic susceptibility follows a Curie-Weiss law between T = 150 and 280 K with a Curie-Weiss temperature θ = ?33 K.     

The temperature dependent thermal and electrical resistivity of high purity silver from 2 to 20 K

The low temperature (T), temperature dependent electrical resistivity (?), and thermal resistivity (ω), have been measured in a sample having a residual resistivity ratio of 10,000: 1. Below approximately 10 K ? ∝ T⁵ and ω ∝ T² — in excellent agreement with theory. Both resistivities are considerably smaller than those obtained by previous workers on less pure samples. Above 10 K the resistivities rise more rapidly with temperature — particularly for ω. The experimentally determined temperature dependent Lorenz number, $\text{L}{}_{\mathrm{i}}\text{=}\text{?}\text{ωT}$ is examined and suggests that the augmentation of the horizontal scattering of electrons by umklapp processes is greater for ω than for ?.     

Production of direct single electrons in proton-nucleus collisions at 13 GeV/c

Direct production of single electrons in proton-nucleus collisions at 13 GeV/c has been measured. A rising $\text{e}\text{π}$ ratio with decreasing p_T above the 10^?4 level is observed for low p_T single electrons. The source of the rising $\text{e}\text{π}$ ratio at low $\text{e}\text{π}$ ratio at low p_T is discussed in connection with the low mass dielectron continuum below the ? mass region.     

Magnetization process and principal magnetic susceptibilities in RbMnF3

The temperature dependence of χ_⊥, initialχ_p (powder), and evaluated χ_∥ for RbMnF₃ are reported for the temperature range of 4.2–106 K. A shallow minimum at $\text{T}\text{T}{}_{\mathrm{N}}\text{? 0.72}$ is observed in χ_⊥. The field dependence of the magnetization shows a smooth rotation of the spins to a normal direction above H_c ? 2.43 kOe at 4.2 K.     

Plasmon energy gain and double ionization satellites in the Be Auger spectrum

Two relatively weak, higher energy satellites are observed at 18 and 38 eV above the Be KVV Auger spectrum. The lower energy satellite is assigned to coupling of energy from bulk plasmon de-excitations $\text{(}\text{h}\text{?}\text{ω ～ 18 eV)}$ with Auger electrons and the higher energy event to Auger electrons ejected from Be atoms with doubly ionized K levels.     

Theory of the input power-dependence of the electron heating in n-inversion layers

The average energy loss P of hot electrons due to the interaction with acoustic bulk phonons is calculated and used to determine the electron heating temperature Δ as a function of the input power eμE². It is found that P creases proportional to Δ² and is independent of the carrier concentration. Consequently the ratio Δ/√ eμE² turns out to be a constant $\text{(0.75 × 10}{}^{\mathrm{?2}}\text{K/(eV/s)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ for $\text{n-Si and 2.04 × 10}{}^{\mathrm{?2}}\text{K/(eV/s)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ for n-GaAs) in agreement with the experimental data deduced from FIR-emission experiments at T = 4.2 K.     

Calculation of repulsive and effective attractive terms of a σ-exciton type mechanism for possible superconductivity in polycytosine

Using ab initio SCF LCAO crystal orbitals for the π electrons of a cytosine stack and corresponding SCF LCAO MOs for the σ orbitals of a cytosine the Coulomb (C) and effective attractive terms (Ã) of a σ-exciton mechanism of superconductivity have been recalculated. The results show that $\text{C ≈ ∥}\text{A}\text{?}\text{∥}$ and for some scattering processes $\text{∥}\text{A}\text{?}\text{∥ > C}$. This suggests that the possibility of such a mechanism for higher temperature superconductivity in this system at least cannot be excluded in the framework of a BCS type theory.     

Pressure effects on the quadrupole coupling constant of 7Li in first stage lithium graphite

The pressure dependence of the experimental ⁷Li NMR spectra is reported for first stage lithium graphite (LiC₆) intercalation compound at temperatures T = 232 and 293 K. This experiment together with the presented point charge model calculation of the ⁷Li quadrupole coupling constant $\text{(}\text{e}{}^2\text{qQ}\text{h}\text{)}$ allows an unambiguous determination of the sign of e²qQ/h which is negative: $\text{e}{}^2\text{qQ}\text{h=-52 kHz}$ at p = 1 bar and T = 232 K. The averaged location of the electrons transferred from the Li intercalant to the graphite layers, as estimated in this study, is in excellent agreement with earlier theoretical energy-band calculations. The compressibility of LiC₆ in the c-direction is predicted to be k_c = 1.7 × 10^-12cm²dyn^-1, it agrees with estimates derived from the available phonon dispersion relations.     

Spin-wave scattering from A γ-Fe47Mn53alloy

Spin waves in the antiferromagnetic alloy γ-Fe_0.5Mn_0.5 have been studied at $\text{295° K(}\text{T}\text{T}{}_{\mathrm{N}}\text{= 0.63)}$ by the inelastic neutron scattering technique. We observed an isotropic dispersion and obtained a value for the spin-wave velocity of 255 ± 30 meV Å (3.88 ± 0.50 × 10⁶ cm/sec), which is the order of the spin-wave velocity in Cr (a typical itinerant antiferromagnet). The energy gap at q = 0 was found to be 7.0 ± 0.5 meV. These results suggest the existence of a long-range spin ordering in the conduction electrons of this alloy.     

Phonon heating by hot electrons in n-InSb in quantizing magnetic fields

The effect of the phonon “narrow throat” was experimentally found in n-InSb in crossed electrical and quantizing magnetic fields at temperatures 1.6—4.2°K. The phenomenon of energy relaxation by hot electrons on phonons was detected with $\text{T}\text{S}\text{?}\text{h}\text{?}\text{λ}{}^{\mathrm{?1}}$ in the case of absence of a phonon thermal tank (S is sound velocity, λ is magnetic length, T is temperature). The value of a critical electric field (E_cr) on the S-type current-voltage characteristic (CVC) was measured as a function of temperature and the magnetic field.     

Adsorption of copper on single crystal planes of tungsten

Properties of copper condensed on selected areas of a thermally cleaned tungsten surface have been studied by probe hole field emission microscopy. Interpretation of the φ_hkl?$\text{}\text{?}$gq relationship observed on (211), (111) and (310) for adsorption at T > 300 K is based on hardsphere models of the plane surfaces upon which the first monolayer of copper raises φ_ithkl, the second reduces it to a minimum value, and the third achieves $\text{}\text{?}$gf_sat on each plane. At T > 300 K the relatively low binding energy of copper on (110) prevents is population below ～2$\text{}\text{?}$gq as previously observed for lead, and the plateaux in the φ₁₁₀?$\text{}\text{?}$gq curves are thought to result from the difficulty of nucleating the first and second monolayers of copper on (110). Comparison of our observations with those made by LEED/Auger techniques emphasise significant differences between the substrates used, in that, on field emitters (110) is step-free and surrounded by a sink/ source of adatoms, while the LEED specimen is stepped but has no comparable local sink/ source. The initial changes in φ are ascribed to formation of an adsorbate-substrate dipole whose sign and magnitude is controlled by electron equilibration between the substrate metal and a broadened and partly-filled resonance level lying approximately 5.2 eV below the vacuum level. Measurement of the total energy distribution of electrons field emitted from (110) and (132) supports this picture which contrasts with that of Polanski and Sidorski who consider the dipole sign and strength to be controlled principally by adsite geometry. Low activation energies characterise surface transport which is controlled by one-plane processes, and in some cases transport across the probed area is controlled by processes of relatively high activation energy which take place outside the examined plane.     

Theory of charge exchange scattering from surfaces

We present a simple model calculation of the charge exchange probability for ions scattering from solid surfaces, including interactions with both broad band delocalized electrons and with localized core electrons within an Anderson type Hamiltonian with time dependent parameters. The results exhibit some of the major observed experimental features, including characteristic oscillations as a function of incident velocity (from quasi-resonant electron interchange with the core levels) and overall exponential decay $\text{～exp}\text{(?A}\text{v)}$, with v the incident ion velocity, from interactions with the broad band electrons.     

Critical strength for ideal incommensurate structures

A concise method is developed to show the following in one dimension: (a) If there is a sharp metal-insulator transition in an ideal sinusoidal incommensurate structure then $\text{W}\text{V = 2}$. (b) There is an infinite dc conductivity of electrons in an ideal incommensurate structure for T = 0 if $\text{W}\text{V < 2}$. (c) Addition of impurities which scatter between all pairs of k values may lead to a finite conductivity for $\text{W}\text{V < 2}$. (It tends to zero as L → ∞). The concept of duality used by Aubry is then extended to the general problem of localization and the breakdown of extended states is illustrated.     

Upper bound of I = 0 exchange in Kπ scattering

Using Kπ phase shifts and ππ inelasticity above $\text{K}\text{K}$ production, we bound the modulus of the $\text{ππ →}\text{K}\text{K}\text{I = 0}\text{S}$ wave below $\text{K}\text{K}$ threshold from Poisson's formula applied to Kπ amplitudes on a family of (s,u) symmetric hyperbolas.     

Hall to drift mobility ratio in Ga1−xAlxAs alloys

Hall concentration measurements as a function of temperature ($\text{750 ? T ? 77}\text{K}$) on n-type epitaxial layers of Ga_1?xAl_xAs in the composition range $\text{0 ? x ? 0.78}$, have been used to evaluate the composite dependence of the Hall to drift mobility ratio in this alloy at 300 K. This ratio is found to be close to unity for alloy compositions $\text{0 ? x ? 0.25}$ and $\text{0.6 ? x ? 0.78}$, but attains a maximum value of 3.8 at x = 0.42 due to the multiconduction Hall effect.     

A search for the I peak at 2.60 GeV/c2 in 12 GeV/c pp interactions in the CERN 2 m HBC

In a study of 12 GeV/c$\text{p}$p interactions in the CERN 2 m HBC, we have searched for a narrow K3π state. Contrary to an investigation of 12 GeV/c$\text{p}$p interactions in the CERN BEBC, we find no support for such a state.     

A small U approach to the 4kF reflections in organic linear chain compounds

It is shown that a lattice distortion of wavevector 4k_F with an essentially one-dimensional correlation occurs in a one-dimensional metal when the intramolecular Coulomb interaction U is small compared with the band-width 4t; ($\text{U}\text{4t}\text{?}\text{1}\text{4}$). This one-dimensional property suppresses the real phase-transition temperature well below the mean-field transition, where fluctuative 4k_F distortions build up. This accounts for the 4k_F reflections observed in TTF-TCNQ and several other charge transfer compounds. The strong locking of the electrons to the lattice when the band is $\text{1}\text{4}$ (or$\text{1}\text{2}$) full, and weak locking when the band is $\text{1}\text{3}$ (or $\text{2}\text{3}$) full, are also accounted for.     

A Regge-pole overview of kaon-nucleon scattering

Regge-pole residues and trajectories have been extracted at fixed-t values in the range $\text{0 ? t ? ?1.0 (}\text{GeV}\text{/c)}{}^{\mathrm{<mtext>2</mtext>}}$ by simultaneously fitting CMSR and measured data on all two-body K(K)N → K(K)N processes for laboratory momenta between 1.5 GeV/c and 280 GeV/c. A good fit to all the data and CMSR is possible provided that an f′ is introduced in the vacuum quantum number exchange amplitude. This explains the possible violation of duality previously seen in this amplitude. Particular attention is paid to the problem of $\text{?-}\text{A}{}_{\mathrm{<mtext>2</mtext>}}$ exchange degeneracy and the role of their secondary trajectories, both in the CMSR and for the line-reversal breaking observed in KN charge exchange.