Conductivite ionique des systemes Kx(Znx/2Ge1-x/2)O2 et Kx(GaxGe1-x)O2 de structure cristobalite

The crystal chemistry of the K_x(Zn_x/2Ge_{1-$\text{x}\text{2}$})O₂ and K_x(Ga_xGe_1-x)O₂ systems has been investigated. In each of them a solid solution with a cristobalite-type structure has been obtained with a 0.90?×?1 range. The K⁺ conductivity increases strongly with vacancy content, while the activation energy remains nearly constant.Influence of various crystal chemical parameters on the conductivity (lattice covalency, size of the bottlenecks, etc...) is discussed.     

Finite-range DWBA analyses of (dt) and (d3He) reactions on 64Zn at Ed = 13 MeV

Exact finite-range DWBA analyses of ($\text{d}\text{, t}\text{)}$ and $\text{(}\text{d}\text{d}$, ³He) reactions have been performed for an ⁶⁴Zr target at an incident deuteron energy of 13.0 MeV, leading to the ground states of the residual nuclei. The microscopic overlap functions for (d, t) and (d, ³He) systems obtained by using the Phillips triton wavefunctions have been used as projectile form factors into the calculation. The results are compared with zero-range DWBA calculations taking the finite-range effects into account by means of a local energy approximation. The results obtained by finite-range and zero-range calculations for differential cross sections as well as vector and tensor analysing powers are compared with the experimental data. The range of validity of the local energy approximation is discussed.     

Structure et proprietes de conduction du compose K0,1Li0,9SbO3

Single-crystals of K_0,1Li_0,9SbO₃ are obtained by ion exchange method from crystals of KSbO₃, $\text{1}\text{6}$ KF and crystallize in the cubic system, space group Pn3, a = 9,681 (3) Å, Z = 4. Using 398 independent reflections, the structure has been refined by full-matrix least squares, to factor R = 0,043.In this space group, the alkaline ions are in an ordered state.The ionic conductivity of cubic KSbO₃ phases is very high and the motion of cations is three-dimensional along <111> tunnels. The authors discusse the influence of ordered (Pn3) and disordered (Im3) states on the conductivity of these compounds.     

Electrical transport and magnetic properties of Nd2(WO4)3

Measurements of the molar magnetic susceptibility (X_m) of a powdered sample of Nd₂(WO₄)₃ in the temperature range 300–900 K, and the electrical conductivity (σ) and dielectric constant (?$\text{)}\text{?}$ of pressed pellets of the compound in the temperature range 4.2–1180 K are reported. X_m obeys the Curie-Weiss law with a Curie constant C= 3.13 K/mole, a paramagnetic Curie temperature θ= ?60 K and a moment of Bohr magnetons, p= 3.49 for the Nd³⁺ ion. The electrical conductivity data can be explained in terms of the usual band model and impurity levels. Both the σ and ?$\text{\$}\text{?}$data indicate some sort of phase transition round 1025 K. The conductivity follows Mott's law $\text{σ = A exp (?B/T}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{)}$ in the temperature range $\text{200 < T < 3000}\text{K with}\text{B = 45.00 (}\text{K}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{and}\text{A = 1.38 × 10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$. The dielectric constant increases slowly up to 600 K, as is usual for ionic solids. The increase becomes much faster above 600 K, which is attributed to space-charge polarization of thermally generated charge carriers.     

Double inelastic interactions in pd collisions in the 1.6–4.3 GeV/c incident p momentum range

We present results on $\text{p}\text{d}$ multiplicity distributions at 3.9 and $\text{4.3}\text{GeV}\text{/c}\text{p}$ incident momenta obtained from a bubble chamber experiment. An excess is observed for the even-prong multiplicities as compared with $\text{p}$ collisions on free protons. This excess as well as that observed in other existing $\text{p}\text{d}$ data in the 1.6–2.9 GeV/c range was analysed in terms of double interaction processes inside the deuteron.     

f72 neutron occupancies in the Ca isotopes

Methods of obtaining nucleon occupancies from total energy-weighted sum rules for spectroscopic factors are described and applied to $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ neutron transfer data for Ca isotopes. The $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ neutron occupancies obtained are consistent with shell model expectations and, for ⁴¹Ca and ⁴³Ca, with values previously obtained from an analysis using non-energy-weighted sum rules.     

Quantum corrections to conductivity of glassy Zr100−xCux alloys

The variation of the conductivity of glassy Zr_100?xCu_x alloys (x=50, 58, 67 and 71) in the temperature range 2–300 K is discussed in some detail. It is shown that the conductivity varies as √T for $\text{T}\text{θ}{}_{\mathrm{D}}\text{3}$ and T for the lower temperatures which is consistent with the predictions of a weak localization theory. Another strong temperature variation of the conductivity sets at the lowest temperatures which could be either due to interaction effects or due to electron scattering on the unstable ionic configurations. Some support to the latter effects is presented.     

Magnetization and exchange constants in Zn1−xMnxSe

Magnetization of Zn_1?xMn_xSe ($\text{x}\text{≤ 0.1}$) was measured for magnetic field up to $\text{B}\text{= 15}\text{T}$ in the temperature range 2.2 – 30 K. The obtained data were described by Brillouin-like function. The direct comparison of magnetization data with the previous magnetooptical data enabled us to determine the s-d exchange constants in $\text{Zn}{}_{\mathrm{<mtext>1?</mtext><mtext>x</mtext>}}\text{Mn}{}_{\mathrm{x}}\text{Se}\text{:}\text{N}{}_{\mathrm{<mtext>o</mtext>}}\text{α = 0.26}\text{eV}$, $\text{N}{}_{\mathrm{<mtext>o</mtext>}}\text{β = ?1.31}\text{eV}$.     

Polarization in n-d scattering at 14.2 MeV

The angular distribution of the analyzing power in ${}^2\text{H(}\text{n}\text{,}\text{n}{}^2\text{H}$ elastic scattering has been measured at a neutron energy of 14.2 MeV in the angular range 50° to 152° c.m. Neutrons with a polarization of approximately 0.5 were obtained from the ${}^3\text{H(}\text{d}\text{n}\text{)}{}^4\text{He}$ reaction at a deuteron energy of 140 keV and lab emission angle of 82°. The ${}^3\text{H(}\text{d}\text{n}\text{)}{}^4\text{He}$ reaction was induced by vector polarized douterons obtained from a source of polarized ions. The latter was of a conventional “atomic beam” type. The results show good agreement with the data on the charge symmetric $\text{p}\text{+}\text{d}$ process at a proton energy of 14.5 MeV. Comparison is also made with the theoretical calculations of Doleschall and of Pieper and a good agreement is found.     

Non-ohmic conductivity of TaS3 in the low-temperature semiconducting regime

Electrical conductivity of the quasi one-dimensional conductor TaS₃ was measured in the low-temperature semiconducting regime. Below 100K, the conductivity along c-axis (l-d axis) in the low field limit is characterized by the activated process with the activation energy of 250K, and the current-field (I-E) characteristic is nonlinear, $\text{dI}\text{dE}$ increasing with the field strength. These results can be explained by the excitation of phase solitons associated with pinned CDW condensates.     

An upper limit for the induced scalar coupling constant ƒs

Recently, two comprehensive works analysing the available extensive data on superallowed Fermi β-decays have been published by Raman-Walkiewicz-Behrens and Hardy-Towner. We reviewed such compilations to investigate (a) the consistency of the data with CVC theory and (b) the sensitivity of the $\text{F}$t values to different ways of evaluating the integrated statistical rate function. No evidence for sizeable mesonic exchange effects was found. It is shown that using the available data for 0⁺ → 0⁺ superallowed transitions it is possible to extract a meaningful upper limit for the induced scalar coupling constant ?_s. For instance, considering the $\text{F}$t values reported by Raman-Walkiewicz-Behrens we obtained $\text{?}{}_{\mathrm{<mtext>s</mtext>}}\text{/?}{}_{\mathrm{<mtext>v</mtext>}}\text{= (?0.14± 1.55) × 10}{}^{\mathrm{?4}}$. The limit imposed by this value is almost one order smaller than the order l/M which one would expect in the case where CVC should not hold.     

Comparison of pp and pp interactions at s = 53 GeV

Results are presented from the first p$\text{p}$ colliding beam runs at the CERN ISR, using the UA5 streamer chamber detector. p$\text{p}$ interactions at $\text{s}\text{= 53}\text{GeV}$ are compared with pp data taken in the same experiment. The results are in good agreement with extrapolations of low-energy p$\text{p}$ data.     

Etude de 17N par la reaction 18O(t, αγ)17N

The first six excited states of ¹⁷N have been studied by using the ¹⁸Ot, αγ)¹⁷N reaction at a bombarding energy of E_t = 3.5 MeV. Alpha-gamma angular correlation measurements (method II) were used to determine spins, mixing ratios and branching ratios. The 1.37, 1.85, 1.91, 2.53, 3.13 and 3.20 MeV levels have been assigned the spins $\text{3}\text{2}$, $\text{1}\text{2}$, $\text{5}\text{2}$^?, $\text{5}\text{2}$⁺, $\text{7}\text{2}$ and $\text{3}\text{2}$ respectively. Excitation energies are also given. Most of the results are in good agreement with previous data or suggested values. Mixing ratios have been obtained for the first time. The level scheme of ¹⁷N is compared with some $\text{T =}\text{3}\text{2}$ analogue states in ¹⁷O and ¹⁷F and with results of recent shell-model calculations.     

Dispersion of surface polaritons at metal surfaces

The dispersion relation for surface polaritons at a vacuum-metal interface has been obtained using a wave-vector-dependent electrical conductivity. Surface polariton attenuation coefficients calculated in the limits of local and extreme nonlocal conductivity vary with frequency ω as ω² and ω^{$\text{7}\text{3}$} respectively.     

Direct inversion of magnetic fluorescence quenching data for the B3Π(Ou+) state of iodine

A direct inversion procedure, developed from predissociation studies, is applied to accurate magnetic quenching data for fluorescence from the $\text{B}{}^3\text{Π}\text{(O}{}_{\mathrm{<mtext>u</mtext>}}{}^{\mathrm{+}}\text{)}$ state of iodine. The repulsive curve obtained is comparable to that derived by numerical evaluation of the relevant Franck-Condon factors.     

Structure,vibrational study and conductivity of the trihydrated uranyl bis(dihydrogenophosphate): UO2(H2PO4)2·3H2O

The X-ray structure (293 K) of UO₂(H₂PO₄)₂·3H₂O has been refined (R = 0.062): M_r = 518g, space group: P2₁/c (Z = 4); $\text{a = 10.816(1)}\text{A}\text{?}$, $\text{b = 13.896(2)}\text{A}\text{?}$, $\text{c = 7.481(1)}\text{A}\text{?}$, β = 105.65(1)^°, $\text{V = 1082.7(2)}\text{A}\text{?}{}^3$; D_c = 3.17 Mg m^?3. The structure consists of infinite chains along the (101) axis with U atoms bridged by two H₂PO₄ groups. The U atom is surrounded by a pentagonal bipyramid of oxygen atoms, one of them being an equatorial water molecule. The cohesion between the chains is ensured by hydrogen bonds involving the two last water molecules. An assignment of IR and Raman bands with isotopic substitution spectra is proposed. A phase transition at 128 K was made evident by DSC and spectroscopy. The room-temperature phase is characterized by a high disorder of the OH bond orientation while in the low-temperature phase H₂O and POH species appear well oriented. The conductivity seems to occur by proton transfer and protonic-species rotation at the POH-water molecular interface between the chains. ac conductivity has been determined by means of the complex-impedance method ($\text{σ}{}_{\mathrm{<mtext>RT</mtext>}}\text{～ (3?12) × 10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$; E ～ 0.20 eV).     

Hopping conductance in electron irradiated n-type GaAs

A.c. conductivity is studied in n-type electron irradiated GaAs at helium temperatures. For T < 25 K variable range hopping $\text{[σ∝exp(-b/T}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{)]}$ is observed. The experimentally observed low values of $\text{b(K}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{)}$ are discussed. At T > 30 K the conductivity exhibits an activation energy of 0.5 meV which is attributed to excitation into an upper band. The frequency dependence of hopping conductance is σ ∝ ω^S with S=1.8 and S=0.9 depending on the degree of radiation induced damage.     

Vacancy-solute binding in Al-Zn alloys

A reanalysis of the resistometric data obtained by Takamura on quenched $\text{Al}$-Zn yields a vacancy-solute binding enthalpy considerably less than Takamura's estimate and more in line with the results of annealing experiments. The value obtained, 0.08 eV, is still about four times larger than estimates from positron annihilation experiments.     

The effect of a magnetic field on the heat conductivity of oxygen and oxygen - argon gas mixtures

The effects of a magnetic field on the heat conductivity of the paramagnetic O₂ and O₂-Ar gas mixtures of different compositions have been studied by using the hot-wire method. The magnetic field has been applied perpendicular to the temperature gradient so that the fractional change ($\text{Δλ}{}^{\mathrm{\perp }}\text{λ}$) of the longitudinal coefficient of thermal conductivity has been measured. For pure O₂, after applying proper corrections the experimental data obtained by using the hot-wire method agreed well with those obtained by using other methods. The experimental ($\text{Δλ}{}^{\mathrm{\perp }}\text{λ}$) data have been interpreted by applying the theory of Knaap and Beenakker and treating O₂ as a mixture of m_s = 0 and m_s = ± 1 states.For O₂-Ar mixtures, the theory of Köhler and Raum has been used and O₂ has been treated as a mixture of m_s = 0 and m_s = ±1 states. By using this approximation, the experimental ($\text{Δλ}{}^{\mathrm{\perp }}\text{λ}$) data have been interpreted fairly well and reasonable values of several cross sections have been obtained.     

A study of states in 201, 203Tl using the (d, 3nγ) reaction: A new 92− band

The nuclei ^{201, 203} Tl were formed in (d, 3n) reactions. Studies of the de-excitation γ-rays are described and level schemes are deduced for both isotopes. Evidence is presented for the existence in ²⁰¹Tl of a rotational band built on the $\text{9}\text{2}{}^{\mathrm{?}}$ isomeric state at 920 keV. The band is compared to the $\text{9}\text{2}{}^{\mathrm{?}}$ bands occurring in the odd isotopes ^{191 ? 199}Tl and is shown to be well described by a symmetric rotor-plus-particle model. The model predictions for the low-lying positive parity states are also considered and satisfactory agreement with experimental data is obtained. No $\text{9}\text{2}$^? band was observed in ²⁰³Tl and possible interpretations of this result are presented.