Mössbauer and infrared spectroscopic studies of novel mixed valence states in cobaltous ferrocyanides and ferricyanides

Novel mixed valence states have been obtained by the treatment of cobaltous ferrocyanides (Co⁺²Fe^II) and ferricyanides (Co⁺²Fe^III) in an ozone flow. The CN stretching bands occur at 2085 cm^–1 for Co⁺²Fe^II and at 2160 cm^–1 for Co⁺²Fe^III. After the ozonization process of Co⁺²Fe^II, an intense band approximately at 2125 cm^–1 is detected. This intermediate band must correspond to a mixed valence state of the type: Fe^II–CN–Co²⁺–NC–Fe^III Mössbauer spectra recorded in situ during the ozonization of Co⁺²Fe^II show the presence of two components: a doublet with isomer shift and quadrupole splitting values close to the cobalti ferricyanide and a very broad line for the mixed valence state. From the Mössbauer and infrared spectra of the aged samples of the Co⁺²Fe^II after ozonization, a relaxation process to the initial state of the samples is observed but the mixed valence state is stable.     

On the structural and magnetic properties of amorphous Fe84−x W x B16 alloys in dependence of W content

A series of rapidly solidificated amorphous Fe_84?x W _x B₁₆ (x=0–5) alloys have been studied. A strictly linear decrease ofH _eff versus concentration of W has been observed by Mössbauer spectroscopy.     

Observation of a diamagnetic signal up to 132 K in a Tl−Ca−Ba−Cu−O compound

Tl–Ca–Ba–Cu–O compounds of the nominal composition of (1, 1, 1, 1) have been prepared from different starting materials and with the same heat treatment process. During the investigation of their properties a diamagnetic signal has been found up to the temperature of 132 K. This hints at the existence of a certain material content distributed into discrete superconducting domains. The parameters of it reflect a superstructure of the (2, 2, 2, 3) and (2, 1, 2, 2) compositions having a time-dependent behaviour. On the basis of the signal levels at 132 K and 4.2 K, the quantity of the high temperature superconducting material is about 0.01% of the total one at liquid He temperatures.     

Finitely additive states and completeness of inner product spaces

For any unit vector in an inner product space S, we define a mapping on the system of all -closed subspaces of S, F(S), whose restriction on the system of all splitting subspaces of S, E(S), is always a finitely additive state. We show that S is complete iff at least one such mapping is a finitely additive state on F(S). Moreover, we give a completeness criterion via the existence of a regular finitely additive state on appropriate systems of subspaces. Finally, the result will be generalized to general inner product spaces.     

Diffractive dissociation reaction np → Λ0K0p for incident neutron momenta between 30 and 70 GeV/c BIS-2 collaboration

We present results of the exclusive diffractive reaction np ⁰K⁰p at 0·08 < |t|< 0·53 GeV²/c² and momenta between 30–70 GeV/c at the Serpukhov neutron beam. Thet-dependence is exp (Bt) withB= 11·4± 2·3 (GeV/c)^–2 and it exhibits the diffractive minimum at ¦t¦ 0·28 GeV²/c² for ⁰K⁰ massesM < 1·8 GeV/c².B decreases with increasingM. Correlation with the beam direction is observed in the rest frame of the ⁰K⁰ system: the cross section rises for the forward-going ⁰. The rise is more pronounced for higherM. The cross section of reaction np ⁰K⁰p for 0<|t|< 0·53 GeV²/c² is 10·3 ± 2·5 ± 2·8 b.     

Low temperature nuclear orientation of239Np in gadolinium host

The angular distribution of γ-radiation from the decay of²³⁹Np oriented at low temperatures in gadolinium host was investigated. The orientation parameters B2 and B4 were determined. The attenuation factors for two long-living states in²³⁹Pu at 391.5 keV and 285.4 keV were calculated. From the anisotropies measured the multipole mixing ratios for 11 gamma-transitions in²³⁹Pu were deduced. The results obtained support the assignment of spins of the levels at 492.2 keV and 391.6 keV as 3/2⁻ and 7/2⁻, respectively.     

Nuclear orientation study of160Tb impurity in gadolinium single crystal

The low temperature nuclear orientation of¹⁶⁰Tb in gadolinium single crystal has been studied in the temperature range 5–60 mK and in the external magnetic field B_ext ≤9 T, applied both in the a- and c-axis directions. The obtained results indicate the noncollinearity between the Tb magnetic moments and the magnetization of the gadolinium matrix.     

The corrosion of weathering steel by SO2 polluted atmospheres at its very early stages

CEMS was used in conjunction with AES to study the protective film formed on a weathering steel by exposure to a highly SO₂-polluted atmosphere. Ferrous species (sulphite) and ferric oxyhydroxides (ferrihydrite and α-FeOOH) were identified as corrosion products. From the correlation of CEMS and AES results the evolution with time of the different compounds is obtained, and a possible reaction sequence is outlined.     

Yttrium aluminate crystals for slabs

The methods of growing YAG:Nd crystals with a flat interface and YAP:Nd crystals with a sharp conical interface are described. The form of the interface was controlled by the He and H₂O content in the reducing atmosphere composed mainly of Ar and H₂ as well as by axial temperature gradient above the melt level. The crystals of 120–180 mm in length were machined to the high-quality slabs.