Raman scattering from electronic excitations of samarium in semiconducting and metallic Sm1−xYxS

The Raman spectra of Sm_1?xY_xS for $\text{x?0.4}$ have been measured. Electronic scattering between the J = 0 ground state and the J = 1 and 2 excited states of Sm²⁺ is observed. The singlet-triplet transition is observed on both sides of the black to gold phase transition in Sm_1?xY_xS.     

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.     

Thermal changes in the optical properties of SnSxSe2−x crystals

Optical measurements on crystals in the series SnS_xSe_2?x for 0 ? x ? 2, have yielded information on the changes in the ordinary refractive index $\text{Δn}\text{ΔT}$ and the energy gap $\text{ΔEg}\text{ΔT}$ in the temperature range 125–425 K. The coefficient $\text{Δn}\text{ΔT}$ has values +40 to +160 × 10^?6K^?1 and this confirms that covalent bonding predominantly exists in these materials. The coefficient $\text{ΔEg}\text{ΔT}$ remains fairly consistent for all values of x with an average value of -8.0×10^-4eV K^-1.     

Thermochemical analysis of PdxAg1-x alloys from XPS core-level binding energy shifts

XPS core level binding energy shifts of the $\text{3d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ energy levels of Pd and Ag for a large number of coevaporated Pd_xAg_1-x alloys with 0?x?1 have been measured. An analysis of the Pd level shifts yields the heats of formation of the PdAg alloy system in good agreement with those reported from calorimetric measurements. Combining these data with the Ag level shifts one obtains the heat of formation of Cd diluted into Pd_xAg_1-x.     

Angular distributions and structure functions from two-jet events at the CERN SPS pp collider

The two-jet cross section measured in the UA1 apparatus at the CERN $\text{p}\text{p}$ Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x₁ and x₂. The angular distribution dσ/d cos σ rises rapidly as cos → 1, independent of x₂ and x₂, as expected in vector gluon theories (QCD). The differential cross section in x₁ and x₂ is consistent with factorization and provides a measurement of the proton structure function $\text{F(x) = G(x) +}\text{4}\text{9}\text{[Q(x) +}\text{Q}\text{(x)]}$ at values of the four-momentum transfer squared, -t? ≈ 2000 GeV². Over the range x = 0.10?0.80 the structure function shows an exponential x dependence and may be parametrized by the form F(x) = 6.2 exp (?9.5x).     

Role of p-d hybridization in the Tc-variation of Y(Rh1−xRux)4B4 superconductors

Auger and photoemission studies for Y(Rh_1?xRu_x)₄B₄ superconductors elucidate the mechanism for the abrupt drop in T_c near x=0.5. The B $\text{p}$-states admix more strongly with Ru than Rh $\text{d}$-states, thereby yielding low-T_c values for Ru-rich compounds due to broadening of the $\text{d}$-band feutures. These effects underlie a previous suggestion that the preservation of Rh₄ tetrahedral units is essential for high-T_c values in ternary boride compounds.     

Lattice dynamics study of the solid solution (Bi1−xLax) FeO3 by i.r. spectroscopy

By i.r. absorption spectral measurements, (Bi_1?xLa_x) FeO₃ solid solution is shown to have phase transitions near x = 0.20; 0.40; 0.75, the range $\text{0.20?x?0.40}$ being of an intermediate nature.     

Evidence for assignment of 14.0 MeV state in 11B from 10B(n,n)10B

The differential cross section and polarization for neutrons scattered from ¹⁰B have been measured at E_n = 2.63 MeV (E_x = 13.85 MeV). The results of this experiment and other available neutron scattering data in the range 1 < E_n < 4 MeV are interpreted through a single-level R-matrix calculation over the region 12 < E_x < 15 MeV. Based on this analysis the most probable J^π assignment for the 14.0 MeV level in ¹¹B is $\text{11}\text{2}{}^{\mathrm{+}}$. The anomaly near E_x = 13.1 MeV can only be explained in terms of two overlapping levels having assignments of ($\text{5}\text{2}$, $\text{7}\text{2}$)^? and ($\text{3}\text{2}$, $\text{5}\text{2}$, $\text{7}\text{2}$)⁺.     

Magnetic hyperfine interaction and curie temperatures of amorphous (FexNi1−x)80P14B6

Amorphous magnetic glasses (Fe_xNi_1?x)₈₀P₁₄B₆ (0.1 ? x ? 1) have been studied by Mössbauer spectroscopy. At 4.2 K, well-defined and very similar spectra have been observed for samples with different Fe concentration. This suggests that the Fe hyperfine field distribution is insensitive to the amount of dilutant. The value of the average hyperfine field at 4.2 K increases with Fe concentration. A value of 232 kOe is obtained by extrapolating to zero Fe concentration. The relationship $\text{H}{}_{\mathrm{eff}}\text{(O) = (232 + 33}\text{μ}\text{)}\text{kOe}$, similar to that of crystalline Fe-Ni alloys describes the results. The values of T_c = 60 K, 234 K and 425 K have been determined for samples with x = 0.125, 0.25 and 0.375 respectively. The T_C vs. x relation suggests a critical concentration of x_c ? 0.1, above which ferromagnetism exists. By fitting the measured values of T_C to the results of a coherent potential approximation, exchange interaction temperatures of J_FeFe = 617 K, J_FeNi = 800 K and J_NiNi ? 0 K have been obtained.     

Magnetic interactions between Fe(III) ions in the solid solutions CuM1 − xFexS2 (M = Al,Ga, In) and AgM1 − xFexO2 (M = Al,Ga).

Magnetic properties of CuM_{1 ? x}Fe_xS₂ (M = Al, Ga, In) and β-AgM_{1 ? x}, Fe_xO₂ (M = Al, Ga) solid solutions have been studied by Mössbauer spectroscopy (only on CuGa _{1 ? x}Fe_xS₂), magnetization measurements and EPR spectroscopy.In the structures studied all ions have tetrahedral co-ordination.The magnetic interactions between Fe(III) ions are shown to be very strong for nn sites ($\text{J}\text{k}$～100 K). More distant exchange interactions are found to fall off rather slowly as the distance between Fe(III) ions increases and are suggested to depend essentially on the number of bonds traversed.     

High ionic conductivity in new fluorine compounds of tin II. II. On the binary system PbF2-SnF2

The Pb_xSn_1?xF₂ solid solutions adopt various structural types following the x value. We observed an evolution from a completely disordered structure for the phases with high lead concentration to an ordered structure for x=0.5. The increase of the logarithm of the conductivity with x is explained by the increase of the number of vacancies in normal anionic positions when the ratio of $\text{Sn}{}^{\mathrm{2+}}\text{Pb}{}^{\mathrm{2+}}$ is increasing.     

The 16O + p → 17F (T = 32) resonances at Ep = 11.26,12.71 and 14.57 MeV

Excitation functions for ¹⁶O+p reactions have been measured with high energy resolution in the region of the first, second and seventh $\text{T =}\text{3}\text{2}$ resonances in ¹⁷F at extreme backward angles. The observed resonance shapes have been analyzed with a single-level resonance formula taking the off-resonance spin-flip amplitude into account. The resonance parameters of the ¹⁷F first $\text{T =}\text{3}\text{2}$ state studied with special emphasis are E_x = 11193.3 ± 2.3 keV, Γ = 200 ± 40 eV and Γ_p0 = 19 ± 3 eV. This result and other results are compared with previous studies and theoretical predictions. The comparison with data of the mirror nucleus ¹⁷O is discussed with respect to the observed charge asymmetry of the isospin-forbidden particle decay widths.     

Charge density wave commensurability in 2H-TaS2 and AgxTaS2

The charge density wave transition in 2H-TaS₂near 75 K has been observed to be incommensurate, using electron diffraction, with $\text{q}{}^1\text{= (}\text{0.338}\text{±}\text{0.002}\text{)a}{}^1{}_0$ along the 〈10.0〉 directions which, within the experimental uncertainty, remains temperature independent to about 14 K. Incommensurate charge density formation is also observed in Ag_xTaS₂ samples for $\text{x?}\text{0.26}$ with an increase in q¹ to $\text{(}\text{0.347}\text{±}\text{0.002}\text{)a}{}^1{}_0$ when x?0.26. Within the experimental error q¹ appears to be temperature independent to 25 K.     

Broken chemical order and phase separation in GexSe1−x glasses

The trend of broken chemical order in Ge_xSe_1?x glasses displays a minimum at $\text{x =}\text{3}\text{8}$; as well as at $\text{x =}\text{1}\text{3}$;. The composition dependence of site populations determined by Mössbauer spectroscopy can be quantitatively understood in terms of molecular phase separation in these glasses. The proposed molecular phases and their morphologies are discussed in terms of a quasi-equilibrium free energy for rapidly quenched-melts. It is shown that this general approach provides a microscopic basis for understanding the overall glass forming tendency not only in binary but also in many ternary chalcogenide glasses.     

Structure study of 12B from the elastic scattering of neutrons from 11B

Differential cross sections for neutrons scattered from ¹¹B have been measured for 2.2 MeV < E_n < 4.5 MeV. The differential cross section σ(θ) is fitted reasonably well by R-matrix parameters for broad states in ¹²B with assignments 1 ^? and (1) ⁺ at excitation energies E_x = 5.8 and 6.8 MeV respectively. The broad 1 ^? state has not been previously observed and is believed to be the 1 ^? member of the $\text{1}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{1}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ particle-hole multiplet predicted to exist by earlier shell model calculations. Its existence completes the identification of all of the levels of this multiplet (3 ^?, 2 ^?, 4 ^?, 1 ^?). The broad (1)⁺ level at E_x = 6.8 MeV has not been previously observed. States at excitation energies E_x = 5.61, 5.73 and 6.6 MeV have been assigned spins and parities of 3⁺, 3^? and (1)⁺ respectively. These states had previously been assigned spins of 2, 3 and $\text{≧ 1}$ respectively. Work on T = 1 states in ¹²C¹ has been compared with the present work.     

Study of isovector charge-exchange excitations and their decay via the 16O(3He,tp) reaction

The nucleus ¹⁶F was studied via the ¹⁶O(³He, t) reaction at 81 MeV. Differential cross sections for many states were obtained and interpreted with DWBA calculations, using microscopic wave functions and an effective projectile-nucleon interaction. Proton decay to several states in ¹⁵O was observed and angular correlations for protons in coincidence with tritons detected at θ = 0° were measured. Several spin-parity assignments have been made. The distribution of isovector ΔL = 1 strength could be deduced. The analog of the giant dipole resonance ($\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{? 9.5}\text{MeV}\text{)}$ is strongly excited. The magnetic quadrupole strength has two strong components, one low, at E_x = 0.424 MeV, and one high, at $\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{? 7.5}\text{MeV}$. Evidence is given for a proportionality between cross section and M2 strength for transitions to J^π = 2^? states, which possibly make the (³He, t) reaction a suitable tool for determining quantitatively isovector M2 (or B_ij) strengths.     

Lambda polarization in inclusive K−p interactions at 10 and 16 GeV/c

A strong negative transverse polarization P_z is found for forward produced lambdas observed in 10 and 16 GeV/c K^?p interactions. This indicates that exchanges of natural spin-parity are dominant in the production process. Using the polarization results, the $\text{d}\text{σ}\text{d}\text{u′}$ distributions for natural and unnatural spin-parity exchanges are derived. For unnatural exchanges, a dip is observed at u′?0.3 GeV², which can be explained as a nonsense-wrong-signature zero of the N_β trajectory. The value of P_z for forward producted lambdas is constant with energy. This is in agreement with the triple-Regge model prediction, as is the fact that P_z is constant as a function of $\text{M}{}^2\text{s}$. The two non-transverse polarization components, P_x and P_y, have been measured and are found to be consistent with zero for all x values, unlike P_z.     

Lithium mobility in the layered oxide Li1−xCoO2

The Li⁺-ion chemical diffusion coefficient in the layered oxide Li_0.65CoO₂ has been measured to be $\text{D}\text{?}\text{= 5 × 10}{}^{\mathrm{?12}}$ m² s^?1 by three independent techniques: (1) from the Warburg prefactor, (2) from the transition frequency for semi-infinite to finite diffusion lengths in steady-state ac-impedence measurements and (3) from a modified Tubandt method that uses ac-impedance data to distinguish interfacial and surface-layer resistances from the bulk resistance of the sample. This value and a small increase in D? with (1 ? x) in Li_1?xCoO₂, 0.45 < (1 ? x) < 0.80, compare favorably with the $\text{D}\text{?}\text{= 5}\text{to}\text{7 × 10}{}^{-12}\text{m}{}^2\text{s}{}^{-1}$ obtained by Honders for this system with pulse techniques. A qualitative discussion is presented as to why this composition dependence and why D? for this system is a factor of five larger than that for Li⁺-ion diffusion in Li_xTiS₂.     

Spectroscopic investigation of [(NH4)xK1−x]2SnCl6 mixed crystals

Polycrystalline samples of the solid solution [(NH₄)_xK_1?x]₂SnCl₆(0?x? 1) have been investigated by DSC, X-ray diffraction and Raman scattering experiments. Substitution of K⁺ by NH⁺₄ depresses the phase transition temperature T₁. For 0? x ?0.05 a linear temperature coefficient $\text{d}\text{T}{}_1\text{dx=?5.16}\text{K/mol}$ % is obtained. The cubic lattice constant roughly obeys Vegard's law, whereas the linewidth of the SnCl₆^2?F_2g internal vibration displays a nonlinear dependence on composition.     

Heat of mixing in HfCxN1−x compounds from XPS core level binding energy shifts

The XPS core level binding energies for the Hf4f_{$\text{7}\text{2}$}, Cls and Nls level in several nearly stoichiometric HfC_xN_1?x compounds are reported. Using the thermochemical model to calculate core level binding energy shifts in metals the heat of mixing as function of the HfC/HfN ratio is calculated from the position of the Cls binding energies. In addition it is shown that the Hf4f_{$\text{7}\text{2}$} and Nls binding energies can be used to obtain further thermochemical data for these compounds.