The influence of strong electric fields on the growth of platinum oxide nanoparticles and their interaction with molecular hydrogen

The influence of strong electric fields created by the tip of a scanning tunnel microscope on the growth, modification, and destruction of platinum oxide nanoparticles and their interaction with molecular hydrogen was studied in high-vacuum experiments by the “nanolaboratory” method. The dependences of the rate of platinum oxidation on the voltage applied to the contact, its polarity in particular, were measured and interpreted. The possibility of field-induced reversible changes in the atomic structure of oxide phases was demonstrated. For the first time, applied field polarity dependent autooscillations of chemical reactions accelerated by the field that occurred in the interaction of molecular hydrogen with PtO _x were observed. The results obtained, which modeled the influence of the charges of small metal particles on their catalytic activity, introduced a new size parameter into the theory of deposited catalysts. This parameter determined maximum sizes of nanoparticles whose reactivity depended on their charge state.     

The influence of plastic deformation on the magnetostriction constant of nickel

The magnetostriction constant of nickel was measured as a function of plastic deformation up to an elongation of 30%. The values of the magnetostriction constant in deformed samples deviate considerably, a fact which cannot be explained by errors of measurement. The absolute value of the magnetostriction constant decreases with increasing plastic deformation (by around 5%).

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30% . , . ( 5%).

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In conclusion the authors thank J. Kaczér, C. Sc. and B. esták, C. Sc. for carefully reading the paper and for their remarks, J. Míová for help in the measurements and workers of the chemical department of our Institute for careful preparation of the samples.     

Hyperfine field and electric quadrupole interaction of51V in YFe2 and HoFe2

Spin echo measurements were made on Y(Fe_0.99V_0.01)₂, (Y_0.97Ho_0.03) (Fe_0.99V_0.01)₂ and Ho(Fe_0.96 V_0.04)₂ compounds. The addition of Ho to YFe₂ causes a spin reorientation from <111> to <100> but this is not reflected in the⁸⁹Y or⁵¹V hyperfine fields. A well resolved⁵¹V NMR line was observed at 51.5 MHz and 60.0 MHz respectively for Y and Ho Laves compounds but with no evidence of quadrupole satellites. Small quadrupole splittings ¦2P_t¦ = 171 ±5 kHz and 178 ±5 kHz respectively for Y and Ho compounds were deduced from the oscillatory decay of the⁵¹V spin echo after a two pulse sequence.On leave from Department of Physics, University College, The University of New South Wales, Australian Defence Force Academy, Campbell, ACT, Australia.     

Nuclear structure study of51V

The spins and electromagnetic properties of levels up to 3,700 keV in⁵¹V were studied by means of inelastic proton scattering. Results are discussed with reference to the many-particle shell model using effective surface delta and realistic Kuo-Brown interactions.     

The influence of plastic deformation on the magnetostriction constant of iron-nickel alloys

The magnetostriction constant of three iron-nickel alloys and one Fe-Ni-Co alloy was measured as a function of the plastic elongation up to about 25%. The magnetostriction constant decreases with deformation in all materials. In Fe-Ni-Co alloy the volume magnetostriction also decreases. The influence of crystallographic texture is discussed and it is shown that it is not a decisive factor. The observed decrease is explained by assuming the influence of lattice deformation on spin-orbital interaction.

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- Fe-Ni-Co 25%. . Fe-Ni-Co . , . .

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In conclusion the authors thank Z. Málek and S. Libovický for carefully reading this paper and for remarks, J. Míová for help in the measurements, J. Cáslavský for X-ray determination of the texture and members of the chemical department of the Institute of Physics for thermal treatment and analysis of the samples.     

Search for M1 strength in 51V and the difference in 51V(e,e′) and 51V(p,p′) spectra

Following the studies of the distribution of M1 strength in the even-even N = 28 isotones ⁴⁸Ca, ⁵⁰Ti, ⁵²Cr and ⁵⁴Fe by inelastic electron scattering, the result of a search for M1 transitions in the odd-even N = 28 nucleus ⁵¹V is reported. No strong M1 excitation has been detected, in contrast to a recent (p, p') experiment. There is no immediate explanation for this discrepancy. Shell-model calculations indicate that a part of it might be accounted for by an interference between the spin and orbital term of the electromagnetic transition operator in the (e, e') experiment.     

The influence of deformation on the reactivity of C=C bonds in reactions with ozone

The influence of strain in the reaction center containing a double bond on double bond reactivity at the first stage of the reaction with ozone was studied by the B3LYP density functional theory method and ab initio MP2, CCSD, QCISD, and MRMP2 multireference methods. The 6-31+G** and 6-311+G** basis sets were used. The reactions of ozone with ethylene and butylene were studied. Deformation (ɛ) was introduced by using the C=C bond length or the distance between extreme carbon atoms as a coordinate not subjected to optimization. Stretching of the double bond was found to activate the reaction by the mechanisms of symmetrical and nonsymmetrical addition. The sensitivities to deformation were similar in the two channels. When the butene fragment as a whole was stretched, a different picture was observed, and the reaction with ozone was decelerated. In both cases, the logarithms of rate constants linearly depended on ɛ. The calculation results were analyzed using the approach developed earlier, which allowed the calculation results to be used to obtain an analytic form of the dependence of activation energy E _a on the strength of bonds and to relate deformation-induced changes in E _a to the length and rigidity of the initial and transition states.     

An electron spectroscopic investigation of the interaction of methanol with polycrystalline aluminum

X-ray and ultraviolet photoelectron spectroscopic results are reported for the interaction of CH₃OH with clean polycrystalline Al in the temperature range 110–500 K. Methanol is moleculary chemisorbed at low exposure and low temperature (110 K) followed by condensation at higher exposure. Bonding mechanisms and geometries in the condensed and chemisorbed layers are discussed. The multilayers desorb beginning near 170 K and the chemisorbed layer is converted into a surface methoxide. Room temperature adsorption also leads to formation of the methoxide species which is stable to ～500 K, at which point it decomposes evolving CH₄ and leaves the surface oxidized.     

Shell-model calculation of51V using pairing-plus-surface-tensor-interaction

Employing⁴⁸Ca as the core, the structure of⁵¹V is studied in the framework of a conventional shell-model. A pairing-plus-surface-tensor-interaction is used as the effective two-body interaction. Besides all configurations arising from 1f _7/2 and 2p _3/2 single-particle orbits, configurations of the form wheren ₁+n ₂=3 (the number of extracore protons) andn ₂ = 1, 2 are also considered. Low-lying energy levels are calculated and a satisfactory agreement with the experimental values is obtained. Our calculated density of states is higher than that reported previously. We also present theB(E2) values for transitions between low-lying levels and the spectroscopic factors for the⁵⁰Ti (³He, d)⁵¹V reaction. The dependence of the interaction parameters on the mass number of the core nucleus is also studied.     

Photospallation of51V at intermediate energies

The yields of⁵¹V(, xpyn) reactions have been measured at maximum bremsstrahlung energies from 75 to 800 MeV. Mean cross sections have been deduced, compared to Monte-Carlo calculations and analysed with a semiempirical Rudstam formula. Total isobaric mean cross sections and anN/Z dispersion curve in the mass regionA = 42–48 have been obtained. The results are in agreement with cascade-evaporation theory and with earlier data obtained with photons and protons.     

Effect of mode interaction on spectroscopic parameters of molecular vibrations with combination frequencies

An equation has been obtained for excited vibrations with combination frequencies by modifying the equation for the normal vibrations of the molecules, using the direct product operation and its properties for the eigenvalues and eigenvectors of the cofactor matrices within matrix perturbation theory. From the solution of the equation, the elements of the vibrational mode tensor are determined, for which formulas are written (in terms of projectors of the matrix of the dynamic coefficients) that take into account their changes for excited vibrations. Using these formulas makes it possible to study the effect of perturbations on the change in the intramolecular and spectroscopic parameters of combination vibrations of the molecules. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 421–425, July–August, 2006.     

光谱及电化学方法研究大黄酸与牛血清白蛋白的相互作用

采用荧光光谱、紫外光谱和圆二色光谱法并结合电化学方法,研究了大黄酸与牛血清白蛋白之间的相互作用。结果表明:大黄酸对牛血清白蛋白有较强的荧光猝灭作用且为静态猝灭,并计算得出不同温度下其结合常数(KA)与结合位点数(n)分别为:3.67×105,0.95(298 K);2.60×104,0.83(309 K)。由热力学参数确定它们间的作用力主要是静电引力,并依据F rster能量转移理论求得其结合距离为3.28 nm,同步荧光光谱及圆二色谱表明大黄酸对牛血清白蛋白的构象产生影响。     

Laser spectroscopic determination of the 50V quadrupole moment

Using the method of atomic-beam magnetic resonance, detected by laser-induced resonance fluorescence (ABMR-LIRF), the atomic ground-state hyperfine intervals of ⁵⁰V were precisely measured. A quadrupole moment ratio $\text{Q(}{}^{50}\text{V}\text{) / (}{}^{51}\text{V}\text{= ?4.03(3)}$ is obtained which results in $\text{Q(}{}^{50}\text{V}\text{) = +0.21(4)}\text{b}$.