Effect of low-level Ge additions on the superconducting transition in PbTe:Tl

A study is reported of the effect of low-level germanium additions (∼0.01–0.1 at. %) on the parameters of the superconducting transition, viz. the critical temperature T _c, the second critical magnetic field H _c2, and in PbTe doped with 2 at. % Tl, which are derived from the dependence of the electrical resistivity of a sample on temperature (0.4–4.2 K) and magnetic field (0–1.3 T). The discontinuity revealed by experimental data is related to the onset of a Ge-induced structural phase transition. Fiz. Tverd. Tela (St. Petersburg) 40, 1204–1205 (July 1998)     

Determination of traces of elements in solutions by the method of flame atomic-ionization spectroscopy

Multistage effective excitation circuits for a sodium atom in a propane-butane-air flame are studied experimentally. Consideration is given to the effectiveness of the excitation and ionization of an Au atom following the collision scheme

Inhomogeneous contact processes on trees

We consider an inhomogeneous contact process on a tree of degreek, where the infection rate at any site isλ, the death rate at any site in isδ (with 0 <δ ⩽ 1) and that at any site in is 1. Denote by the critical value for thehomogeneous model (i.e.,δ=1) on and byϑ(δ, λ) the survival probability of the inhomogeneous model on . We prove that whenk > 4, if , a subtree embedded in , with 1 ⩽σ ⩽ √k, then three existsδ _c ^σ strictly between ( ) and 1 such that ( ) whenδ >δ _c ^σ andϑ(δ, λ _c( ) > 0 whenδ <δ _c ^σ ; ifS={o}, the origin of , then for anyδ ε (0, 1).     

Magnetic field effect on free and bound excitons in chalcopyrite CuInS<Subscript>2</Subscript>

The effect of a strong magnetic field (induction up to 10 T) on free and bound excitons in CuInS₂ single crystals is studied. A diamagnetic shift to higher energies is observed in the luminescence and reflectance spectra for free-exciton lines A_LPB ≈ 1.5348 eV, A_UPB ≈ 1.5361 eV, and BC ≈ 1.557 eV. The diamagnetic shifts of free-exciton lines A_LPB, A_UPB, and BC provide a basis for estimating the exciton reduced masses = 0.131m₀, = 0.13 4m₀, and μ_BC = 0.111m₀, respectively. Bound-exciton lines in luminescence spectra are split under the influence of the magnetic field. The magnitude of the Zeeman effect (g-factor of the magnetic splitting) is estimated. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 373–377, May–June, 2007.     

Nuclear moments of neutron deficient iridium isotopes from laser spectroscopy

Laser spectroscopy measurements have been performed on neutron deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d⁷6s^{2 4}F_9/2 → 5d⁷6s6p ⁶F_11/2 at 351.5 nm have been studied for the ^182–189Ir, and ^191,193Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the HFS measurements and the changes of the mean square charge radii from the IS measurements. A large mean square charge radius change between ¹⁸⁷Ir and ¹⁸⁶Ir and between and has been observed. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Ginzburg-Landau expansion and the slope of the upper critical field in disordered superconductors

It is shown that the slope of the upper critical field in superconductors with d pairing drops rapidly with increasing concentration of normal impurities, while in superconductors with anisotropic s pairing increases and reaches the well-known asymptotic level characteristic for the isotropic case. This difference makes it possible, in principle, to employ measurements of H _c 2 in disordered superconductors as an experimental method for determining the type of pairing in high-T _c superconductors and systems with heavy fermions. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5, 347–352 (10 March 1996)     

Measurement of the mass and width of the W boson

The mass and width of the W boson are measured using e⁺e^– → W⁺W^– events from the data sample collected by the OPAL experiment at LEP at centre-of-mass energies between 170 GeV and 209 GeV. The mass (m_W) and width (Γ_W) are determined using direct reconstruction of the kinematics of W⁺W^– → and W⁺W^– → events. When combined with previous OPAL measurements using W⁺W^– → events and the dependence on of the WW production cross-section at threshold, the results are determined to be

Dependence of the Electronic Spectra of the Chlorin Molecule on the Degree of Alternation of the Macrocycle Bond Lengths

The geometric structure of the chlorin molecule (H₂Ch) has been calculated by the restricted and unrestricted Hartree-Fock (RHF and UHF) methods with an AM1 Hamiltonian. Transformations of this molecule into excited electronic states have been calculated by the CNDO/S method. The RHF method without symmetry restrictions gives a plane structure for the chlorin macrocycle with an alternation of the lengths of the bonds along the 18-member azacyclopolyene and a C_1h symmetry for the molecule as a whole. The level of the first excited state Q₁ of this structure is substantially shifted (δ ≅ +4000 cm⁻¹) relative to the Q_x level of porphin (H₂P) toward shorter waves, which is in contradiction with the experimental data, according to which this shift is long-wave and is equal to δ = −400 to −550 cm⁻¹. The optimization of the geometry of H₂Ch by the UHF method has shown that it has a structure with an 18-member azacyclopolyene with bonds of equal lengths and a D_2h symmetry. For this geometry of H₂Ch the calculated shift of the Q_x level, equal to δ = −70 cm⁻¹, is bathochromic and the position of the Q_y level is practically exactly coincident with the experimental one. For the geometry calculated by the RHF method with restrictions on the D_2h symmetry of the 18-member azacyclopolyene δ = +180 cm⁻¹, and for the geometry calculated with restrictions on the highest C_2v symmetry of the H₂Ch molecule δ = +620 cm⁻¹. The latter result shows that the “natural” requirement for the C_2v symmetry of the H₂Ch macrocycle, which is frequently used in various calculations, is inadequate to achieve a quantitative agreement between the calculation and experimental data and, in this case, the lengths of the bonds along the 18-member azacyclopolyene are not equal. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 339–347, May–June, 2005.     

Kinetics of Prompt Fluorescence Decay in Rubrene Films. Manifestations of the Migration of T Excitons

The kinetics of fast fluorescence decay in organic semiconductors due to the splitting of the excited singlet state S₁ into a pair of triplet (T) excitons is significantly influenced by the process of reverse TT annihilation. It is shown that a correct interpretation of this effect requires taking into account the stochastic migration of T excitons. A two-state model (TSM) is proposed for describing the effect of migration on the kinetics of TT annihilation and, thus, on the kinetics of the fission of the S₁ state. In the TSM, the migration effect is interpreted in terms of transitions between the [TT] state of the interacting excitons (at small T?T distances) and the [T + T] state of freely diffusing excitons (at large T?T distances). Within the framework of the TSM, an analytical expression for the fluorescence decay kinetics (FDK) \(I_{S_1 } (t)\) from the S₁ state is derived. This expression is used to describe the FDK measured in amorphous rubrene films in the absence of the magnetic field (B = 0) and in the magnetic field B = 8.1 kG. Adjusting the parameters of the model makes it possible to reproduce the experimentally measured FDK with good accuracy. An analysis of the theoretical FDK obtained revealed a significant contribution of T migration to \(I_{S_1 } (t)\), which manifests itself, in particular, in the characteristic dependence \(I_{S_1 } (t) \sim t^{ - 3/2}\) at long times.     

Mechanism of singlet-oxygen induced delayed fluorescence of bacteriopheophytin in laser excitation

The relative intensity of photosensitized phosphorescence of singlet oxygen (¹O₂) at 1270 nm (L₁₂₇₀) and¹O₂-induced delayed fluorescence (L_df) of bacteriopheophytin a (BPh) (770 nm) in air-saturated solutions of BPh in hexafluorobenzene in excitation by 337-nm pulses of a nitrogen laso is investigated. It is established that L_df≪L₁₂₇₀. The ratio of the initial intensity of delayed fluorescence and phosphorescence of¹O₂(L_df)₀/(L₁₂₇₀)₀ changed from 0.02 to 0.30 as a function of the energies of laser pulses (2.5–5.0 mJ/cm¹) and the BPh concentration (6–18 μM). As the index of quantum efficiency of the delayed fluorescence, the authors used the coefficient

Mach’s principle and hidden matter

According to the Einstein-Mayer theory of the Riemanniann space-time with Einstein-Cartan teleparallelism, the local Lorentz invariance is broken by the gravitational field defining Machian reference systems. This breaking of symmetry implies the occurrence of “hidden matter” in the Einstein equations of gravity. The hidden matter is described by the non-Lorentz-invariant energy-momentum tensor satisfying the relation . The tensor is formed from the Einstein-Cartan torsion field given by the anholonomy objects, F_Aik=2h_A[i,k], and appears together with Hilbert’s energy-momentum tensor T^* _ik and Poincaré’s pressure λg_ik on the right-hand side of Einstein’s equations so that one has

Influence of solar flares on neutrino oscillations

The solar neutrino problem is considered within the framework of a model based on the gauge group SU(2)_L×SU(2)_R×U(1)_B−L. An evolutionary equation is found for the eight-component wave function and a scheme for possible resonant transitions is determined with allowance for the Majorana nature of the neutrino. The influence of solar flares on the oscillation pattern of the neutrino flux is investigated. Yankya Kupala State University, Grodno. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 116–120, June, 1996.     

The hyperfine and isotope structure of the Cd intercombination line – revisited

Careful analysis of the intercombination 5¹S₀–5³P₁ line of the ¹¹³Cd isotope with two hfs components and was carried out. The hyperfine splitting of this line was determined to uncertainty less than 10^-3 cm^-1 using neon-perturbed Doppler limited spectra.     

Evaluation ofS,T, U parameters, triple gauge boson vertices and some oblique corrections in extraU(1) superstring inspired model

Explicit evaluation of the following parameters has been carried out in the extraU (1) superstring inspired model: (i) As Mz₂ varies from 555 GeV to 620 GeV and (m _t) CDF = 175.6 ± 5.7 GeV (Table 1): (a) S^New varies from -0.100 ± 0.089 to -0.130 ± 0.090, (b) T^New varies from -0.098 ± 0.097 to -0.129 ± 0.098, (c) U^New varies from -0.229 ± 0.177 to -0.253 ± 0.206, (d) Τ_z varies from 2.487 ± 0.027 to 2.486 ± 0.027, (e) A_LR varies from 0.0125 ± 0.0003 to 0.0126 ± 0.0003, (f) A _FB ^b remains constant at 0.0080 ± 0.0007. Almost identical values are obtained for (m _t)D0 = 169 GeV (see table 2). (ii) Triple gauge boson vertices (TGV) contributions: AsMz ₂ varies from 555 GeV to 620 GeV and (m _t) CDF = 175.6 ±5.7 GeV. (a)√s = 500 GeV, asymptotic case: varies from -0.301 to -0.179; varies from -0.622 to -0.379; varies from +0.0061 to 0.0056; varies from -3.691 to -2.186. varies from +0.270 to +0.118; varies from +0.552 to 0.238; varies from +0.0004 to +0.0002; remains constant at -0.110. (b)√s = 700 GeV, asymptotic case: varies from -0.297 to -0.176; varies from -0.609 to -0.370; varies from -0.0082 to -0.0078; varies from -3.680 to -2.171.√s = 700 GeV, nonasymptotic case: varies from -0.173 to -0.299; varies from-0.343 to -0.591; varies from -0.005 to -0.011; remains constant at -0.110. The pattern of form factors values for√s = 1000, 1200 GeV is almost identical to that of√s= 700 GeV. Further the values of the form factors for (m _t)D0 (=169 GeV) follow identical pattern as that of (m _t) CDF form factors values (see tables 5, 6, 9, 10). We conclude that the values of all the form factors with the exception of these of , are comparable or larger than theS, T values and therefore the TGV contributions are important while deciding the use of extraU (1) model for doing physics beyond standard model.     

Optical Properties of Amorphous Films of an a-Si<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>x</Subscript>:H Solid Solution with Different Concentrations of Hydrogen

The IR absorption spectra of hydrogenated amorphous films of an a-Si_0.60Ge_0.40:H solid solution that were obtained by plasmachemical deposition at different partial pressures of hydrogen have been investigated. The oscillator strengths Γ that depend substantially on have been determined. It is shown that hydrogen is contained in the films mainly in the GeH and SiH forms. Using integral absorptions I_w, the concentrations of hydrogen were determined. The highest value of is observed at Γ = 0.51, P = 4.16, N_H = 9.7·10²¹ cm⁻³, and C^H = 23.7 at.%. It has been established that the oscillator strengths depend on the hydrogen concentration: they decrease on hydrogen effusion and increase with the hydrogen concentration. It is shown that the hydrogen concentration in the films of the a-Si_0.60Ge_0.40:H solid solution can be controlled by changing its pressure. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 371–376, May–June, 2005.     

Limit Laws and Recurrence for the Planar Lorentz Process with Infinite Horizon

As Bleher (J. Stat. Phys. 66(1):315–373, 1992) observed the free flight vector of the planar, infinite horizon, periodic Lorentz process {S _n ∣n=0,1,2,…} belongs to the non-standard domain of attraction of the Gaussian law—actually with the $\sqrt{n\log n}As Bleher (J. Stat. Phys. 66(1):315–373, 1992) observed the free flight vector of the planar, infinite horizon, periodic Lorentz process {S _n ∣n=0,1,2,…} belongs to the non-standard domain of attraction of the Gaussian law—actually with the scaling. Our first aim is to establish his conjecture that, indeed, converges in distribution to the Gaussian law (a Global Limit Theorem). Here the recent method of Bálint and Gou?zel (Commun. Math. Phys. 263:461–512, 2006), helped us to essentially simplify the ideas of our earlier sketchy proof (Szász, D., Varjú, T. in Modern dynamical systems and applications, pp. 433–445, 2004). Moreover, we can also derive (a) the local version of the Global Limit Theorem, (b) the recurrence of the planar, infinite horizon, periodic Lorentz process, and finally (c) the ergodicity of its infinite invariant measure. Dedicated to Ya.G. Sinai on the occasion of his seventieth birthday. Research supported by the Hungarian National Foundation for Scientific Research grants No. T046187, NK 63066 and TS 049835, further by Hungarian Science and Technology Foundation grant No. A-9/03.     

Effect of bridging aza-substitution on electronic structure and spectral-luminescent properties of isobacteriochlorin NH-isomers

We have investigated the spectral characteristics, quantum yield ϕ_F, lifetime τ_F, and polarization of fluorescence of NH-isomers of dibenzobarrelene disubstituted tetraazaisobacteriochlorin at 293 and 77 K. The following information has been obtained from low-temperature measurements: 1) the weak shoulder on the edge of the long-wavelength 0-0 absorption band disappears at 77 K and, therefore, can be assigned to the cis-NH-isomer [the principal component of the tautomeric mixture is the trans-isomer a (b)]; 2) the low value of ϕ_F at room temperature is due to temperature-viscosity quenching whereas ϕ_F at 77 K is close to 1 and τ_F = 5.3 nsec; 3) the energy of the weak electronic transition G → Q₂ and the interval have been determined. Quantum-chemical calculations found that replacing the methine bridges by nitrogen stabilizes the non-aromatic trans-isomer a (b) whereas the non-planarity of the macrocycle and the alternation of bond lengths increase for the cis-isomers. The calculated electronic absorption spectra of the a isomer reproduce rather well the experimental data. It is shown that the four-orbital model is applicable for the lower excited states Q₁ and Q₂ for all NH-isomers. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 395–407, May–June, 2007.