Experimental test of special relativity by laser spectroscopy

The Doppler-free laser-spectroscopic frequency measurement of Doppler-shifted optical lines in forward and backward direction of a fast ion beam permits a sensitive test of the relativistic Doppler-formula and, hence, the relativistic time dilation factor . An experiment on metastable ⁷Li⁺, stored at a velocity of v = 0.064c in the Heidelberg heavy-ion storage ring TSR, has confirmed time dilation with unprecedented accuracy. Latest tests at two different ion-velocities (v = 0.03c and v = 0.064c) will enhance these measurements. An improved version of this experiment will be carried out at the experimental storage ring (ESR) at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt. The ESR permits ⁷Li⁺ to be stored at v = 0.33c which promises an improvement of the sensitivity to deviations from γ _SR by an order of magnitude. A first test at the ESR has shown the feasibility for this kind of experiment.     

Diffusion of proton in alumina-rich nonstoichiometric magnesium aluminate spinel

The phenomenon of the diffusion of proton and deuteron in a single crystal of magnesium aluminate spinel was studied by infrared absorption. The chemical diffusion coefficient of proton was determined by the relaxation time of the absorption intensity upon the substitution of deuteron with proton. The temperature dependence of the chemical diffusion coefficient of proton for was expressed as . The chemical diffusion coefficient of proton was found to be independent of the composition of spinel and of the atmosphere. Paper presented at the 11th Euro Conference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15 2007.     

A-site deficient lanthanum-calcium chromite-titanates doped with 3d transition metals: synthesis,oxygen nonstoichiometry,electrical conductivity,and catalytic activity

Six (M = Cr, Mn, Fe, Co, Ni, Cu) and two (M = Ni, Cu) single-phase compositions were prepared by conventional solid-state reactions. Oxygen nonstoichiometry, electrical conductivity, phase transformations under reduction-reoxidation at high temperatures and catalytic activity for hydrocarbons oxidation of these compositions were investigated in a wide temperature and oxygen partial pressure range. The Cu-, Ni-, Co-, and Fe-containing compositions are decomposed in reducing Ar/H₂O/H₂ atmosphere with pH₂O / pH₂ = 0.3 at 1,000 °C, while the Cr- and Mn-containing ceramics remain stable at the same conditions. The metallic particles of the added 3d elements formed after decomposition were registered by X-ray diffraction method in case of Cu- and Ni-containing compositions. These formed composites can be completely reoxidized with formation of initial compositions by treatment in air at 1,000 °C. The electrical conductivity of the ceramics investigated in air and Ar/H₂O/H₂ gas flow increases with rising M content. The highest catalytic activity for oxidation of CH₄ and C₃H₆, which was comparable with the activity of the composite, shows the Cu-containing powders. Dedicated to Prof. Dr. Werner Weppner     

Search for new oxide-ion conducting materials in the ceria family of oxides

We have adopted a modified combustion route, namely, a mixed fuel process (MFP) to prepare a novel series of nano-crystalline single- and multiple-doped ceria compositions with controlled powder characteristics, large surface area, finer particle size, high sinterability, and high oxide ion conductivity at intermediate temperatures (500–700 °C). Using the mixed fuel process, we have prepared nano-particles of single- and multiple-doped ceria powders with dopants such as Ca, Gd, and Sm and a suitable combination of the same. In the pursuit for identifying new oxide-ion-conducting materials in this family of oxides, we have pursued the idea of co-doping effect on the single doped compositions with proper introduction of a second dopant. Effect of these dopants on the thermal decomposition and physico–chemical characteristics of the precursor and the powders prepared thereby were studied in detail. Finally, the effects of multiple co-doping on the microstructural and electrical properties were compared to understand the origin of the effect of dopant characteristics on the oxide ion conductivity of Ce_1−x M _x O₂ solid solutions. Our experimental results established unequivocally that co-doping is very effective in identifying new materials with remarkably high ionic conductivity with substantial reduction in the cost for technological applications. Among the studied compositions, the maximum conductivity with minimum activation energy was observed for the triply co-doped CCGS composition (; E _a = 0.56 eV), which is much higher compared to the conductivity exhibited by most of the reported co-doped ceria compositions. In conclusion, an effective way to improve the oxide ion conductivity of ceria-based oxides by proper choice of dopants and co-doping is achieved.     

Chemical stability of hydroxysulphate green rust synthetised in the presence of foreign anions: carbonate, phosphate and silicate

Hydroxysulphate green rust species were precipitated in the presence of various anions. is stable at ∼pH 7 and is transformed into a mixture of magnetite and ferrous hydroxide when the pH raised at ∼12. In the presence of carbonate species, is partially transformed into a mixture of magnetite and siderite at ∼pH 8.5. This transformation is stopped when silicate anions are present in the solution. As already observed for phosphate anions, the adsorption of silicate anions on the lateral faces of the crystals may explain this stabilization effect. Sulphate anions are easily exchanged by carbonate species at ∼pH 10.5. In contrast, anionic exchange between sulphate and phosphate anions was not observed.     

Critical behavior of La0.67−y (Sr, Ba, Ca)0.33+y Mn1−x Sn x O3 (x = 0.01, 0.02, y = 0, 0.07) perovskites

The magnetic critical behavior of the manganese perovskite series $ {\text{La}}_{{0.67 - y}} {\left( {{\text{Sr,}}\,\,{\text{Ba,}}\,\,{\text{Ca}}} \right)}_{{0.33 + y}} {\text{Mn}}_{{1 - x}} {\text{Sn}}_{x} {\text{O}}_{3} The magnetic critical behavior of the manganese perovskite series (x = 0.01, 0.02, y = 0, 0.07) is studied by means of dc magnetic measurements and ¹¹⁹Sn M?ssbauer spectroscopy. The structure can be described by a rhombohedral unit cell (space group R–3C) for the samples where the A-site is occupied by La and Sr or La and Ba ions and orthorhombic unit cell (space group Pnma) for the samples where the A-site is occupied by La and Ca ions. Arrott and scaling plots show that the samples, where the A-site is occupied by La and Sr or La and Ba ions, follow the behavior of a conventional second-order ferromagnetic transition. In contrast, the samples that contain La and Ca ions in the A-site show anomalous behavior around Curie point. M?ssbauer measurements show two magnetic phases below T _c. One of them exhibits stronger exchange interactions with more rapid electron transfer between Mn³⁺/Mn⁴⁺, compared to the other.     

Oxygen ion transport numbers: assessment of combined measurement methods

Several modifications of the faradaic efficiency and electromagnetic field (EMF) methods, taking electrode polarisation resistance into account, were considered based on the analysis of ion transport numbers and p-type electronic conductivity of ceramics at 973–1,223 K. In air, the activation energies for p-type electronic and oxygen ionic transport are 115 ± 9 and 71 ± 5 kJ/mol, respectively. The oxygen ion transference numbers vary in the range 0.992–0.999, increasing when oxygen pressure or temperature decreases. The apparent electronic contribution to the total conductivity, estimated from the classical faradaic efficiency and EMF techniques was considerably higher than true transference numbers due to a non-negligible role of interfacial exchange processes. The modified measurement routes give reliable and similar results when p(O₂) values at the electrodes are high enough, whilst decreasing the oxygen pressure leads to a systematic error for all techniques associated with measurements of concentration cell EMF. This effect, presumably due to diffusion polarisation, increases with decreasing temperature. The most reliable results in the studied p(O₂) range were provided by the modified faradaic efficiency method.     

Coherent pion production in neutrino and antineutrino interactions on nuclei of heavy freon molecules

Studying the coherent diffractive production of pions in neutrino and antineutrino scattering off the nuclei of freon molecules we have observed for the first time in one experiment all three states of the isospin triplet of the axial part of the weak charged and neutral currents. For the corresponding cross sections we derive $$\begin{array}{*{20}c} {\sigma _{coh}^v (\pi ^ + ) = (106 \pm 16) \cdot 10^{ - 40} {{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } {\left\langle {nucl.} \right\rangle }}} \right. \kern-\nulldelimiterspace} {\left\langle {nucl.} \right\rangle }}} \\ {\sigma _{coh}^{\bar v} (\pi ^ - ) = (113 \pm 35) \cdot 10^{ - 40} {{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } {\left\langle {nucl.} \right\rangle }}} \right. \kern-\nulldelimiterspace} {\left\langle {nucl.} \right\rangle }}and} \\ {\sigma _{coh}^v (\pi ^0 ) = (52 \pm 19) \cdot 10^{ - 40} {{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } {\left\langle {nucl.} \right\rangle }}} \right. \kern-\nulldelimiterspace} {\left\langle {nucl.} \right\rangle }}} \\ \end{array} $$ . Comparing our data with theoretical predictions based on the standard model of weak interactions we find reasonable agreement. Independently from any model of coherent pion production we determine the isovector axial vector coupling constant to be |β|=0.99±0.20.     

Search for double electron capture of 106Cd

A search for double electron capture of ¹⁰⁶Cd was performed at the Modane Underground Laboratory (4800 m w.e.) using a low-background and high-sensitivity multidetector spectrometer TGV-2 (Telescope Germanium Vertical). New limits on β ⁺/EC, EC/EC decays of ¹⁰⁶Cd were obtained from preliminary calculations of experimental data accumulated for 4800 h of measurement of 10 g of ¹⁰⁶Cd with enrichment of 75%. They are > 9.1 × 10¹⁸ yr, > 1.9 × 10¹⁹ yr for transitions to the first 2⁺, 511.9 keV excited state of ¹⁰⁶Pd, and > 1.3 × 10¹⁹ yr, > 6.2 × 10¹⁹ yr for transitions to the ground 0⁺ state of ¹⁰⁶Pd. All limits are given at 90% C.L. The text was submitted by the authors in English.     

Measurement of Seasonal Variations of Horizontal Muons with Underground LVD Setup

The Large-Volume scintillation Detector commonly known as LVD and located at the Gran Sasso Laboratory at an average depth of 3650 m w.e. measures muons of intensity $$3.31\times 10^{-4}$$ m$${}^{-2}$$ s$${}^{-1}$$. The results obtained from an analysis of the properties of seasonal variations of the horizontal and vertical muon fluxes are presented in this article. Horizontal muons detected in LVD mostly correspond to rock depths of about 5 km w.e. and zenith angles $$\theta$$ of about $$75^{\circ}$$, while vertical muons ($$\theta\approx 13^{\circ}$$) correspond to depths of about 4.6 km w.e.     

Calculation of the Width of the τ → K–K 0 ντ Decay in the Extended Nambu–Jona-Lasinio Model with Estimation of the Contribution from the Final-State Interaction

JETP Letters - The partial width of the $$\tau \to {{K}^{ - }}{{K}^{0}}{{\nu }_{\tau }}$$ decay has been calculated within the extended Nambu–Jona-Lasinio model including the contact and...     

τ → K–π0ντ Decay in the Nambu–Jona-Lasinio Model Including the Final-State Interaction of Mesons

JETP Letters - The $$\tau \to {{K}^{ - }}{{\pi }^{0}}{{\nu }_{\tau }}$$ decay has been described within the Nambu–Jona-Lasinio model including the contact term and the contribution from an...     

Der Einfluß der Wärmebewegung auf die Breite einer Mössbauerlinie über den Dopplereffekt zweiter Ordnung

AtT=0 a perfect Mössbauer line has natural line widthΓ=?/τ _n . However, with rising temperature the width increases. The reason of the line broadening is the second order Doppler effect which causes a stochastic frequency modulation of theγ-radiation, reflecting the thermal motion of the Mössbauer atom. Following Josephson in treating the second order Doppler shift as a mass changeΔM=E _n/c² of theγ-emitting atom caused by the loss of nuclear excitation energy E _n , and using the well known relaxation formalism for calculating theγ-frequency spectrum, the line broadeningΔ Γ is evaluated within the framework of harmonic lattice theory. For a parabolic lattice frequency spectrum with Debye-temperature Θ one obtains $$\Delta {\Gamma \mathord{\left/ {\vphantom {\Gamma \Gamma }} \right. \kern-\nulldelimiterspace} \Gamma } = \left( {{{\tau _n } \mathord{\left/ {\vphantom {{\tau _n } {\tau _c }}} \right. \kern-\nulldelimiterspace} {\tau _c }}} \right) \cdot \left( {{{E_n } \mathord{\left/ {\vphantom {{E_n } {Mc^2 }}} \right. \kern-\nulldelimiterspace} {Mc^2 }}} \right) \cdot F\left( {{T \mathord{\left/ {\vphantom {T \Theta }} \right. \kern-\nulldelimiterspace} \Theta }} \right),where\tau _c = {{\rlap{--} h} \mathord{\left/ {\vphantom {{\rlap{--} h} k}} \right. \kern-\nulldelimiterspace} k}\Theta $$ is the correlation time of the lattice vibrations. The functionF(T/Θ) may be expanded in powers ofT/Θ, yielding $$F\left( {{T \mathord{\left/ {\vphantom {T \Theta }} \right. \kern-\nulldelimiterspace} \Theta }} \right) = 9720\pi \left( {{T \mathord{\left/ {\vphantom {T \Theta }} \right. \kern-\nulldelimiterspace} \Theta }} \right)^7 forT<< \Theta $$ and $$F\left( {{T \mathord{\left/ {\vphantom {T \Theta }} \right. \kern-\nulldelimiterspace} \Theta }} \right) = 2.7\pi \left( {{T \mathord{\left/ {\vphantom {T \Theta }} \right. \kern-\nulldelimiterspace} \Theta }} \right)^2 forT > > \Theta $$ , respectively. Although unavoidable, the line broadening is obviously too small to be observable by means of the present experimental technique.     

Self-diffusion in α-Fe2O3 natural single crystals

Measurements of¹⁸O self-diffusion in hematite (Fe₂O₃) natural single crystals have been carried out as a function of temperature at constant partial pressure a_{O 2}=6.5·10^?2 in the temperature range 890 to 1227 °C. The a_{O 2} dependence of the oxygen self-diffusion coefficient at fixed temperature T=1150 °C has also been deduced in the a_{O 2} range 4.5·10^?4 - 6.5·10^?1. The concentration profiles were established by secondary-ion mass spectrometry; several profiles exhibit curvatures or long tails; volume diffusion coefficients were computed from the first part of the profiles using a solution taking into account the evaporation and the exchange at the surface. The results are well described by $$D_O \left( {{{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } s}} \right. \kern-\nulldelimiterspace} s}} \right) = 2.7 \cdot 10^8 a_{O_2 }^{ - 0.26} \exp \left( { - \frac{{542\left( {{{kJ} \mathord{\left/ {\vphantom {{kJ} {mol}}} \right. \kern-\nulldelimiterspace} {mol}}} \right)}}{{RT}}} \right)$$ From fitting a grain boundary diffusion solution to the profile tails, the oxygen self-diffusion coefficient in sub-boundaries has been deduced. They are well described by $$D''_O \left( {{{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } s}} \right. \kern-\nulldelimiterspace} s}} \right) = 3.2 \cdot 10^{25} a_{O_2 }^{ - 0.4} \exp \left( { - \frac{{911\left( {{{kJ} \mathord{\left/ {\vphantom {{kJ} {mol}}} \right. \kern-\nulldelimiterspace} {mol}}} \right)}}{{RT}}} \right)$$ Experiments performed introducing simultaneously¹⁸O and⁵⁷Fe provided comparative values of the self-diffusion coefficients in volume: iron is slower than oxygen in this system showing that the concentrations of atomic point defects in the iron sublattice are lower than the concentrations of atomic point defects in the oxygen sublattice. The iron self-diffusion values obtained at T>940 °C can be described by $$D_{Fe} \left( {{{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } s}} \right. \kern-\nulldelimiterspace} s}} \right) = 9.2 \cdot 10^{10} a_{O_2 }^{ - 0.56} \exp \left( { - \frac{{578\left( {{{kJ} \mathord{\left/ {\vphantom {{kJ} {mol}}} \right. \kern-\nulldelimiterspace} {mol}}} \right)}}{{RT}}} \right)$$ The exponent - 1/4 observed for the oxygen activity dependence of the oxygen self-diffusion in the bulk has been interpreted considering that singly charged oxygen vacancies V _O ^? are involved in the oxygen diffusion mechanism. Oxygen activity dependence of iron self-diffusion is not known accurately but the best agreement with the point defect population model is obtained considering that iron self-diffusion occurs both via neutral interstitals Fe _x ⁱ and charged ones.     

Small magnetic polaron effect in lithium iron phosphates

The small polarons in LiFePO₄ are associated with the presence of Fe³⁺ ions introduced by the native defects in relative concentration in the samples known to be optimized with respect to their electrochemical properties. The nearest iron neighbours around the central polaron site are spin-polarized by the indirect exchange mediated by the electronic charge in excess. These small magnetic polarons are responsible for the interplay between electronic and magnetic properties that are quantitatively and self-consistently analysed. Comparison is made with other magnetic polaron effects in other members of the family of magnetic semiconductors to which this material belongs. Paper presented at the 11th Euro-Conference on Science and Technology of Ionics, Batz-sur-Mer, France, 9–15 September 2007.     

τ → K–ηντ Decay in the Extended Nambu–Jona-Lasinio Model Including the Final-State Interaction

JETP Letters - The width of the $$\tau \to {{K}^{ - }}\eta {{\nu }_{\tau }}$$ decay has been calculated within the extended Nambu–Jona-Lasinio model including the final-state interaction of...     

Electron paramagnetic resonance and spinlattice relaxation of Cu2+ ions in ZnSeO4·6H2O

In this paper, we present detailed studies of the EPR spectra of Cu²⁺ ions in single crystals of ZnSeO₄·6H₂O. We describe the spectrum with a rhombic spin Hamiltonian with the following parameters: g_z=2.427; g_y=2.095; g_x=2.097; A _z ⁶⁵ =138.4·10^?4 cm^?1; A _x ⁶⁵ =22.3·10^?4 cm^?1. We studied spin-lattice relaxation in the temperature range 4–300 K at the frequency v≈9.3 GHz. The measured spin-lattice relaxation rate for the orientation H∥L₄ is described well at T<5 K by a linear dependence, while at T>5 K it is described by the sum of three exponentials: $$T_1^{ - 1} = 0.27T + 3.3 \cdot 10^{\text{s}} \exp \left( {\frac{{ - 69.5}}{T}} \right) + 2.6 \cdot 10^7 \exp \left( {\frac{{ - 140}}{T}} \right) + 1.36 \cdot 10^{10} \exp \left( {\frac{{ - 735.6}}{T}} \right){\text{ sec}}^{{\text{ - 1}}} $$ .We discuss possible reasons for the exponential dependence of T ₁ ^?1 for the Raman process.     

Determination of heavy quark non-perturbative parametersfrom spectral moments in semileptonic B decays

Moments of the hadronic invariant mass and of the lepton energy spectra in semileptonic B decays have been determined with the data recorded by the DELPHI detector at LEP. From measurements of the inclusive b-hadron semileptonic decays, and imposing constraints from other measurements on b- and c-quark masses, the first three moments of the lepton energy distribution and of the hadronic mass distribution, have been used to determine parameters which enter into the extraction of |V_cb| from the measurement of the inclusive b-hadron semileptonic decay width. The values obtained in the kinetic scheme are: and include corrections at order 1/m_b³. Using these results, and present measurements of the inclusive semileptonic decay partial width of b-hadrons at LEP, an accurate determination of |V_cb| is obtained: Received: 26 April 2005, Revised: 16 September 2005, Published online: 16 November 2005     

Mössbauer Study of Microstructure and Magnetic Properties (Co,Ni)–Zr Substituted Ba Ferrite Particles

The β-NMR of short-lived β-emitter in a rutile TiO₂ single crystal has been measured as functions of temperature and external magnetic field. Atomic motion induced spin lattice relaxation was observed for two known sites, O substitutional and interstitial sites. The data were analyzed in terms of the thermal atomic jump, which suggests that the motion of defects around the substitutional ¹²N atom for O, and of the interstitial ¹²N atom are attributed to the spin lattice relaxation. The electric field gradients have shown temperature dependence for both sites, which is probably due to the thermal expansion of rutile.