Heat capacity behaviour of Pu−Fe eutectic alloy (10 a/o Fe) between 15 and 373°K. Evidence for order-disorder and an antiphase structure below room temperature

Low temperature heat capacity studies of Pu?Fe eutectic alloy (10 a/o Fe) have suggested the possibility of order-disorder of atoms and an antiphase structure below room temperature. Slow cooling and temperature cycling below 76°K were required for appearance of the postulated antiphase structure. Fermi surface-Brillouin zone boundary interactions are suggested as an explanation for the low temperature behavior of the eutectic alloy as well as for the resistivity maximum in both Pu₆Fe and α-Pu. The best values for S°(298) and {H°(298)?H°(0)} were judged to be 14·20±0·10 cal mol^?1 K^?1 and 1660±30 cal mol^?1.     

Measurement of intensities of multiplets in the 2ν3-band of methane at low temperatures

The integrated intensities of the multiplets P(1)–P(10), R(0)–R(9), and of the Q-branch in the 2ν₃-band of ¹²CH₄ have been measured at 102°K, 152°K, 202°K, 251°K, and 300°K. Comparison of our data with theoretical line strengths confirms, at all of the temperatures mentioned, the intensity anomalies observed by Margolis⁽⁵⁾ for lines in this band. The integrated intensity of the 2ν₃-band is found to be S_v = (1·76±-0·04)(300/T (°K)) cm^?2 atm^?1.     

Decay of 0 2 + states in88,92,94Zr andE0 systematics of Zr isotopes

Branching ratios ofE0 andE2 transitions depopulating the 0 ₂ ⁺ states of^{88, 92, 94}Zr have been determined using conversion-electron and γ-ray spectroscopy. Two different lifetime-measurement methods were applied in the remeasurement of the half-lives of the 0 ₂ ⁺ states in^{92, 94}Zr, yielding consistent results ofT _1/2(0 ₂ ⁺ ,⁹²Zr)=85(15) ps andT _1/2(0 ₂ ⁺ ,⁹⁴Zr)=280(40) ps. The monopole strengths extracted areρ ²(⁹²Zr)=8.4(17) ×10^?3 andρ ²(⁹⁴Zr)=11.9(20)×10^?3. The proton configurations of the 0 ₂ ⁺ states are discussed in view of these values and proton transfer data.     

Ferroelectric and optical properties of Ba6Ti2Nb8O30 single crystals

The dielectric, optical and non-linear optical properties of Ba₆Ti₂Nb₈O₃₀ single crystals were examined from room temperature up to the Curie temperature of 245°C. The spontaneous polarization at room temperature was estimated as 0·22±0·01 C/m². The linear electrooptic constants were measured as r₃₃^T=(1·17±0·02)×10^?10 and r₁₃^T=(0·42±0·01)×10^?10 m/V. The non-linear optical coefficients were d₃₃=(15·1±2·0)×10^?12 and d₃₁=(11·0±2·0)×10^?12 m/V, which are comparable to those of Ba₄Na₂Nb₁₀O₃₀. Temperature dependences of δ₃₃ and δ₃₁ (Miller's δ) were found to be proportional to that of P_s.     

Optic-mode coupling in ferroelectric gadolinium molybdate

Separate measurements of the A₁(TO) and A₁(LO) Raman spectra of ferroelectric gadolinium molybdate at 80°K and above have elucidated the origin of the anomalous temperature dependence of the two lowest frequency lines in the A₁(TO) spectrum. The observed behavior is postulated to be the result of coupling among modes at 44.5, 51.5, and 83 cm^?1 (at 80°K). The 44.5 and 83 cm^?1 modes become the degenerate, soft zone-boundary modes of the paraelectric phase while the 51.5 cm^?1 mode changes to B₂ symmetry. The two lowest frequency lines are the same as those observed previously in i.r. absorption.     

Possible shape-change observed at high spin in123Cs

The collective moment of inertia ? _band ⁽²⁾ of¹²³Cs produced in the¹¹⁵In+¹²C reaction at 80 MeV has been measured by gamma-gamma energy correlation techniques. The variations of ? _band ⁽²⁾ with the rotational frequency are compared to those of¹²²Xe and analysed in the frame of a cranked Nilsson-Strutinsky model. We conclude that the addition of one proton to the triaxial (γ?30°)¹²²Xe core gives a final prolate-type nucleus¹²³Cs withγ?0° above a rotational frequency?ω?0.55 MeV.     

Raman study of WO3 thin films

The influence of substrates, thermal treatment and coloration-bleaching cycles on the structure of WO₃ thin films used in electrochromic devices has been investigated by Raman microscopy. Films (2000–8000 Å) were prepared by RF sputtering from a metallic tungsten target at a constant pressure (5 × 10^?3Torr) of pure oxygen or a mixture of Ar20% O₂. They are amorphous, transparent and electrochromic. Thermal treatment at 360°C produces crystallization. Modifications of the WO₃ framework are also induced by coloration-bleaching cycles.     

高能电子对原子核C12的弹性散射

In this paper, we have calculated the elastic scattering of high energy electrons with nuclei C¹² by phase shift calculation.We take the charge distribution of the nucleus C¹² as following:(1) exponential distribution:ρ(x)=ρ₀θ^-x/a, (2) gaussian distribution:ρ(x)=ρ₀e^(-x2/a2),(3) uniform distribution: ρ(x) ={ρ₀ when 0kR, where a and b are the parameters, and the constant R is the radius of the nucleus C¹². The energy of the electrons is 187 Mev.The result of the calculation shows that the gaussian distribution confirms the experimental result better than the other two kinds of distributions, and gives R=(12)^1/3r₀, where r₀=1.35×10^-13 cm.     

Study of theω π + system

The mass spectra of theω π ⁰ system, produced inπ ^? p charge-exchange reactions at 38 GeV/c and 100 GeV/c, show a new neutral state with a mass of 2200±20 MeV and a width of 260±50 MeV. Likeρ ₃(1690), this meson,X(2200), is produced through one-pion-exchange.X(2200)J ^PC is likely 1^??. It might be a 2³ D ₁ radial-orbital excitation ofρ ⁰. Its production cross section falls with energy quadratically, in agreement with one-pion-exchange. The cross sections forb ₁(1235) andρ ₃(1690) production have also been measured; their energy dependences have been determined.     

Exotic states X ±(1600, I G (J PC)=2+ (2++)) in photoproduction reactions

It is shown that the list of unusual mesons that are planned to be studied in photoproduction reactions can be supplemented with I ^G (J ^PC)=2⁺ (2⁺⁺) exotic states X ^±(1600), which are natural to seek as manifestations of the ρ^±ρ⁰ decay channels in the reactions γN → ρ^±ρ⁰ N and γN → ρ^±ρ⁰Δ. A classification of the ρ^±ρ⁰ states according to their quantum numbers is presented. A model for the spin structure of the amplitudes for the reactions γp → f ₂(1270)p, γp → a ₂ ⁰ (1320)p, and γN → X ^±(N, Δ) is proposed, and estimates are obtained for the corresponding cross sections. At E _γ≈6 GeV, it is found that σ(γP → f ₂(1270)p)≈0.12 μb, σ(γp → a ₂ ⁰ (1320)p)≈0.25 μb, σ(γN → X ^± N → ρ^±ρ⁰ N) ≈ 0.018 μb, and σ(γp → X ⁻Δ⁺⁺ → ρ⁻ρ⁰Δ⁺⁺≈0.031 μb. The problem of isolating signals from X ^± states against the natural background that is associated with other channels of π^±π⁰π⁺π⁻ production is discussed. It is deduced that searches for exotic states X ^±(2⁺ (2⁺⁺)) in experiments at JLAB will be quite efficient—for example, the yield of about 2.8×10⁶ events per month is expected to correspond to the estimated cross sections for the reactions γN → X ^± N → ρ^±ρ⁰ N. __________ Translated from Yadernaya Fizika, Vol. 63, No. 10, 2000, pp. 1904–1912. Original Russian Text Copyright ? 2000 by Achasov, Shestakov.     

Bose-Einstein condensation in an exactly soluble system of interacting particles

The model investigated recently by Tóth, a lattice gas of bosons with hard-core repulsion on a complete graph, is studied here by diagonalizing the Hamiltonian. The thermodynamic free energy per site is shown to bef, where $$\beta f = \beta \rho ^2 + \mathop {Min}\limits_{0 \leqslant x \leqslant Min(\rho , 1 - \rho )} \left\{ {\beta x(1 - x) + x\log x + (1 - x)\log (1 - x)} \right\}$$ whereβ is the inverse temperature andρ∈[0, 1] is the number of particles per site. This formula is equivalent to the one obtained by Tóth. There is a phase transition atβ +β ^* (ρ) = (1?2ρ)^?1 log[(1?ρ)/ρ]. Ifβ?β ^*(ρ), Bose-Einstein condensation is shown to be present, the condensate density (number of condensed particles per site) in the thermodynamic limit being [ρ?x ^*][l?ρ?x ^*], wherex ^* is the minimizing value ofx, satisfyingβ ^*(x ^*)=β.     

Absence of premelting phenomena in pure perfect gallium crystals revealed by Debye-waller-factor measurements using anomalous diffraction of X-rays

Premelting phenomena have been searched for in pure, perfect gallium crystals by using anomalous X-ray transmission. The temperature dependence of the integrated intensity under the Bragg peak does not reveal any deviations from its normal behaviour, i.e. an essentially linear increase of the mean square vibrational amplitude of the lattice atoms as a function of temperature between 10 °C and a temperature at least 10^?4 °C close to the melting temperatureT _m =29.75 °C. The temperature dependence of the integrated intensity of the 020-reflection can be described by a Debye temperatureΘ ₍₀₂₀₎=189±6 K. Premelting effects could not be detected.     

Iodine as a donor in CdS

Iodine doped single crystals of CdS were grown from the vapor phase. High temperature Hall effect measurements for the crystals equilibrated with Cd and S₂ vapors at temperatures between 700 and 1000°C gave the free electron concentration as a function of p_Cd or p_S2 and temperature. The results can be explained on the basis of a model in which the CdS is saturated with iodine at low p_Cd (=high p_S2) but unsaturated at high p_Cd.The solubility of iodine in CdS is given by c_t=1·73×10²²p_S2^?1/8 exp (?1·045 eV/kT) cm^?3 atm^?1/8=4·62×10¹⁹p_Cd^1/4 exp (?0·195 eV/kT) cm^?3 atm^1/4The formation of pairs (I_SV_Cd)′ from I_S^· and V_Cd″ is governed by the equilibrium constant K_{P(I, V)}=4 exp (≤1·1 eV/kT)If Cd diffusion occurs primarily by free vacancies, the Cd^* tracer self diffusion leads to a vacancy mobility of (1·2±0·5)×10^?5 cm² sec^?1 at 900°C, in agreement with results reported by Woodbury [12], but (7±3) times larger than reported by Kumar and Kroger [10].     

Relation of contact densities with Mössbauer isomer shifts for 35.46 keV M1 transition of125Te

The internal conversion electron and Mössbauer isomer shifts associated with the 35.46 keV M1 transition of¹²⁵Te were observed for different metal samples into which radioactive¹²⁵I as probe atoms were introduced by means of ion-implantation. From the correlation between the Mössbauer isomer shifts and intensity ratios of O shell to N_I shell conversion electrons, a relation between 5s-electron contact densityp _5s(0) in a.u. and isomer shift δ in mm/s was deduced to bep _5s(0)=106+30.3 δ±4.3[(δ?0.30)²+0.069]^1/2, where δ was measured relative to ZnTe in mm/s. The change of the nuclear charge radius in the 35.46 keV M1 transition of¹²⁵Te was found to be ΔR/R=(0.85±0.12)×10^?4 (corresponding to Δ<r ²>=(3.7±0.5)×10^?3 fm²) when a theoretical 4s-electron contact density of 928 a.u. was used.     

Polymer electrolytes based on polycarbonates and their electrochemical and thermal properties

Polycarbonates (4a–d) with various side chain lengths were synthesized by the reaction of 1,4-bis(hydroxyethoxy)benzene derivatives and triphosgene in the presence of pyridine. The polymer electrolytes composed of 4a–d with lithium bis(trifluoromethanesulfonyl)imide (LiN(SO₂CF₃)₂, LiTFSI) were prepared, and their ionic conductivities and thermal and electrochemical properties were investigated. 4d-Based polymer electrolyte showed the highest ionic conductivity values of 1.0?×?10^?4?S/cm at 80 °C and 1.5?×?10^?6?S/cm at 30 °C, respectively, at the [LiTFSI]/[repeating unit] ratio of 1/2. Ionic conductivities of these polycarbonate-based polymer electrolytes showed the tendency of increase with increasing the chain length of oxyethylene moieties as side chains, suggestive of increased steric hindrance by side chains. Unique properties were observed for the 4a(n?=?0)-based polymer electrolyte without an oxyethylene moiety. All of polycarbonate-based polymer electrolytes showed good electrochemical and thermal stabilities as polymer electrolytes for battery application.     

Rigorous treatment of metastable states in the van der Waals-Maxwell theory

We consider a classical system, in a ν-dimensional cube Ω, with pair potential of the formq(r) + γ ^v φ(γr). Dividing Ω into a network of cells ω₁, ω₂,..., we regard the system as in a metastable state if the mean density of particles in each cell lies in a suitable neighborhood of the overall mean densityρ, withρ and the temperature satisfying $$f_0 (\rho ) + \tfrac{1}{2}\alpha \rho ^2 > f(\rho ,0 + )$$ and $$f''_0 (\rho ) + 2\alpha > 0$$ wheref(ρ, 0+) is the Helmholz free energy density (HFED) in the limit γ→ 0; α = ∫ φ(r)d ^v r andf ₀ (ρ) is the HFED for the caseφ = 0. It is shown rigorously that, for periodic boundary conditions, the conditional probability for a system in the grand canonical ensemble to violate the constraints at timet > 0, given that it satisfied them at time 0, is at mostλt, whereλ is a quantity going to 0 in the limit $$|\Omega | \gg \gamma ^{ - v} \gg |\omega | \gg r_0 \ln |\Omega |$$ Here,r ₀ is a length characterizing the potentialq, andx ? y meansx/y → +∞. For rigid walls, the same result is proved under somewhat more restrictive conditions. It is argued that a system started in the metastable state will behave (over times ?λ ^?1) like a uniform thermodynamic phase with HFED f₀(ρ) + 1/2αρ², but that having once left this metastable state, the system is unlikely to return.     

TSC study of electric dipole relaxations in chlorapatite

Electric dipole relaxations in chlorapatite, Ca₅(PO₄)₃Cl, have been studied with the fractional polarization mode of the thermally stimulated currents (TSC) method. Fifty-one of the fifty-seven sets of data obtained in the range 10–443°K fell naturally into four groups yielding compensation temperatures T_C of T_C1, = 202°C, T_C2: = 202°C, T_C3 = 420°C and T_C4= 644°C, with estimated error < 10°C, and characteristic relaxation times τ_C of τ_C1 = 1.3 × 10^?7s, τ_C2 = 3.2 × 10^?6s, τ_C3 = 8.8 × 10^?5s and τ_C4 = 2.3 × 10^?4s. Atomic-scale physical models involving Cl^? ion motion are offered for the 202°C compensation at the temperature of the reported monoclinic-to-hexagonal phase transition and for the 420°C compensation, at which temperature the Cl^? ions individually are thought to have enough thermal energy to maintain the hexagonal form dynamically.     

Ionic conductivity of Zr1−xIn2xO2−x

As x in Zr(In)O_2?x is increased from 0.08 to 0.16 (9–19 mole per cent In₂O₃) the activation energy E(x) for ionic conduction increases from 1.05 to 1.51 eV; the concuctivity decreases from 2 × 10^?5 to 3 × 10^?6Ω^?1cm^?1at 400°C, is composition-independent at about 580°C, and increases from 1 × 10^?2 to 4 × 10^?2Ω^?1cm^?1 at 800°C. The pre-exponential term of the Boltzmann-type conductivity equation depends exponentially on E(x), a much stronger dependence on x than theoretically expected with a model for ionic conductivity that includes nearest-neighbor defect interactions. Analysis of reported conductivity data for Zr(M)O_2?x (M = Sc, Y, Ca and rare earth metals) and other doped oxide electrolytes with fluorite-type structure reveals that the same relationship is observed with these materials when x γ0.08. It is shown that ionic conduction in these oxides is consistent with nearest neighbor vacancy-cation defect interaction forx < 0.08 but that an additional complex interaction with composition-dependent free energy ΔG(x) occurs when xγ 0.08.The lattice constant of Zr(In)O_2?x with the cubic fluorite-type structure is independent of composition, 5.114 ± 0.002 Å, in agreement with ionic size considerations.     

The influence of annealing temperature and tellurium (Te) on electrical and dielectrical properties of Al/p-CIGSeTe/Mo Schottky diodes

p-CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂ type thin films were synthesized by thermal evaporation method on Mo coated glass substrates. To obtain Al/CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂/Mo Schottky diode structure for two compositions of x = 0.0 and 0.6, Al metal was evaporated on upper surface of CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂ as a front contact. Al/p-CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂/Mo structures were annealed temperature range from 150 °C to 300 °C for 10 min under vacuum. The electrical and dielectrical properties of Al/p-CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂ (CIGSeTe) Schottky barrier diodes (SBD) have been investigated. Capacitance–Voltage (C–V) characteristics, Conductance–Voltage (G/w–V) characteristics and interface state density were studied in order to obtain electrical and dielectrical parameters. The effects of interface state density (N_ss), series resistance (R_s), the dielectric constant (?′), dielectric loss (?″), dielectric loss tangent (tan δ), ac electrical conductivity (σ_ac) and carrier doping densities were calculated from the C–V and G/w–V measurements and plotted as a function of annealing temperature. It was observed that the values of carrier doping density N_A for annealing temperature at 150 °C decreased from 2.83 × 10⁺¹⁵ cm^?3 to 2.87 × 10⁺¹⁴ cm^?3 with increasing Te content from x = 0.0 to 0.6. The series resistance for x = 0.0 found to be between 10 and 75 Ω and between 50 and 230 Ω for x = 0.6 in the range of annealing temperature at 150–300 °C.     

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.