Optical constants of silicon in the range of 30–10000 cm<Superscript>–1</Superscript>

A spectrophotometric method of determining the optical constants of materials is proposed that is based on the correction of absorption in spectra. With this method, specimens of silicon of different grades have been examined. The refractive index and the absorption coefficient of silicon in the spectral range of 30–10000 cm^–1 have been determined.     

Search for a Neutrino with a Mass of 0.01–1.0 MeV in Beta Decays of <Superscript>144</Superscript>Ce–<Superscript>144</Superscript>Pr Nuclei

Spectra of electrons from beta decays of ¹⁴⁴Ce–¹⁴⁴Pr nuclei have been measured and analyzed in order to find a contribution from a heavy neutrino. For the neutrino with the mass m_νH in the interval of 150–350 keV, a new upper bound |U_eH|² ≤ (2?5) × 10^?3 at 90% C.L. has been found for the mixing parameter.     

Cross sections for the photofission of <Superscript>243</Superscript>Cm, <Superscript>245</Superscript>Cm, <Superscript>249</Superscript>Bk,and <Superscript>249</Superscript>Cf isotopes in the energy range from the threshold to 10–12 MeV

The relative method was used to measure the photofission cross sections for ²⁴³Cm and ²⁴⁹Cf isotopes in the energy range from 6 to 12 MeV, for ²⁴⁵Cm in the energy range from 5 to 10 MeV, and for ²⁴⁹Bk in the energy range from 5.5 to 10 MeV. The measurements were performed with an energy step of 50 to 200 keV by using the microtron installed at the Institute of Physics and Power Engineering (Obninsk). The cross section for ²³⁸U photofission was used as a reference in these measurements. Data on the cross sections for ²⁴³Cm, ²⁴⁵Cm, and ²⁴⁹Bk photofission were obtained for the first time, while data on the cross section for ²⁴⁹Cf photofission were obtained for the first time only in the energyregion E<10 MeV. The data on the ²⁴⁵Cm nucleus suggest that, in the energy region around 6 MeV, the cross section for its photofission has a maximum, which is likely to be due to the low-energy resonance structure of the dipole-photoabsorption cross section. For ²⁴⁹Cf, an anomalously large value of the photo fission cross section is observed in the region of the first maximum of the giant dipole resonance (E≈11 MeV). By comparing the energy dependences obtained for the fissilities of the ²⁴³Cm and ²⁴⁹Bk isotopes from photofission data with the fissilities from direct-reaction data, it is found that the observed fission thresholds agree and that there is a plateau-like dependence at energies above 7.5 MeV. For the ²⁴⁵Cm and ²⁴⁹Cf nuclei, there are no similar data for performing such a comparison. Data on the fissilities as obtained from the present series of relative measurements that employ the microtron bremsstrahlung spectrum are analyzed.     

Finite Size Effect for the First-Order Phase Transition of the Three-Dimensional Blume-Capel Model on a Cellular Automaton

The first-order phase transition of the three-dimensional Blume-Capel model is investigated using the cooling algorithm which is improved from Creutz Cellular Automaton at D/J = 2.9, i.e. a ratio of single-ion anisotropy constant to bilinear interaction energy. We test the efficiency of the algorithm and obtain the finite-size effects at the first-order phase transition point. The transition temperature is estimated using the probability distributions of the order parameter and the energy. The analysis of data at the transition point indicates that the magnetic susceptibility and the specific heat maxima increase with the system value （L^d）.     

Entropy squeezing for a two-level atom in the Jaynes－Cummings model with an intensity-depend coupling

We study the squeezing for a two-level atom in the Jaynes－Cummings model with intensity-dependent coupling using quantum information entropy, and examine the influences of the initial state of the system on the squeezed component number and direction of the information entropy squeezing. Our results show that, the squeezed component number depends on the atomic initial distribution angle, while the squeezed direction is determined by both the phases of the atom and the field for the information entropy squeezing. Quantum information entropy is shown to be a remarkable precision measure for atomic squeezing.     

Concept of an Electron–Positron Collider for Production and Study of the (μ<Superscript>+</Superscript>μ<Superscript>–</Superscript>) Bound State

The possibility of producing and studying thus far unobserved dimuonium atoms (μ⁺μ^?) using low-energy colliding е⁺е^? beams is considered. Possible collider implementations are discussed, processes affecting its efficiency are investigated, and its parameters are estimated. The collider can probably also be used for high-luminosity experiments on the study of π^± and η mesons.     

Elliptic flow in the nuclear interaction of an astroparticle with an energy of ∼10<Superscript>16</Superscript> eV

A total of 107 cascades formed by secondary particles of the nuclear interaction of an astroparticle with an energy of ～10¹⁶ eV are detected in a stratospheric emulsion chamber. Their azimuthal distribution revealed a distinct anisotropy. The elliptic flow coefficient V₂ was estimated at 0.35 ± 0.02. The average transverse momentum of cascades in the direction of the impact parameter exceeded 3 GeV/c.     

Phase Transition for the Maki–Thompson Rumour Model on a Small-World Network

We consider the Maki–Thompson model for the stochastic propagation of a rumour within a population. In this model the population is made up of “spreaders”, “ignorants” and “stiflers”; any spreader attempts to pass the rumour to the other individuals via pair-wise interactions and in case the other individual is an ignorant, it becomes a spreader, while in the other two cases the initiating spreader turns into a stifler. In a finite population the process will eventually reach an equilibrium situation where individuals are either stiflers or ignorants. We extend the original hypothesis of homogenously mixed population by allowing for a small-world network embedding the model, in such a way that interactions occur only between nearest-neighbours. This structure is realized starting from a k-regular ring and by inserting, in the average, c additional links in such a way that k and c are tuneable parameters for the population architecture. We prove that this system exhibits a transition between regimes of localization (where the final number of stiflers is at most logarithmic in the population size) and propagation (where the final number of stiflers grows algebraically with the population size) at a finite value of the network parameter c. A quantitative estimate for the critical value of c is obtained via extensive numerical simulations.     

Geometric Phase in the Interaction of a Time-Dependent Light Field with <Emphasis Type=Italic>ℑ</Emphasis><Superscript>(3)</Superscript> System

By using of the invariant theory, we have studied the geometric phase in the interaction of a time-dependent light field with ℑ ⁽³⁾ system, the dynamical and geometric phases are given, respectively. The disappearing condition of the geometric phase is given.     

Study of the reaction π–<Emphasis Type="Italic">A</Emphasis> π<Superscript>+</Superscript>π<Superscript>–</Superscript>π<Superscript>–</Superscript><Emphasis Type="Italic">A</Emphasis> at large statistics with VES setup

Partial wave analysis of the π–A π⁺π^–π^– system produced by 29 GeV/cπ^– beam on a beryllium target is presented. About 30 × 10⁶ |events in the wide t′|range 0–0.8 GeV²/c ² are collected with upgraded VES setup. The size of the data sample is 2.5 times larger than one previously analyzed by VES. Data are analyzed using formalism of the density matrix with unlimited rank. We discuss status of the a ₁(1420) a ₂(1700) a ₃(1875) states and a structure of exotic ρ(770)π P-wave with J ^PC = 1^-+. Parameters of a ₃(1875) are estimated as M = 1985 ± 20 MeV/c ², Γ = 200 ± 50 MeV/c ² (preliminary).     

Effective three-body interactions in the α-cluster model for the <Superscript>12</Superscript>C nucleus

Properties of the lowest 0⁺ states of ¹²C are calculated to study the role of three-body interactions in the α-cluster model. An additional short-range part of the local three-body potential is introduced to incorporate the effects beyond the α-cluster model. There is enough freedom in this potential to reproduce the experimental values of the ground-state and excited-state energies and the ground-state root-mean-square radius. The calculations reveal two principal choices of the two-body and three-body potentials. Firstly, one can adjust the potentials to obtain the width of the excited 0₂⁺ state and the monopole 0₂⁺↦0₁⁺ transition matrix element in good agreement with the experimental data. In this case, the three-body potential has strong short-range attraction supporting a narrow resonance above the 0₂⁺ state, the excited-state wave function contains a significant short-range component, and the excited-state root-mean-square radius is comparable to that of the ground state. Next, rejecting the solutions with an additional narrow resonance, one finds that the excited-state width and the monopole transition matrix element are insensitive to the choice of the potentials and both values exceed the experimental ones.     

On Precision Measurement of the Frequency of the 1<Superscript>1</Superscript><Emphasis Type="Italic">S</Emphasis>–2<Superscript>3</Superscript><Emphasis Type="Italic">S</Emphasis> Forbidden Transition of a Helium Atom

The possibility is demonstrated of a precision frequency measurement for the 1¹S₀?2³S₁ forbidden transition (at 62.6 nm) of a helium atom using the stimulated Raman scattering method. The 1¹S₀ singlet state is the ground state of ⁴He, while the metastable 2³S₁ state has the lowest energy in the triplet part of the spectrum (⁴He*). The transition has a very small natural width, which allows us to consider it as a possible reference for creation of a frequency standard in the vacuum ultraviolet region.     

Two-neutrino double- β decay of 94 ⩽ A ⩽ 110 nuclei for the 0<Superscript>+</Superscript> → 0<Superscript>+</Superscript> transition

The two-neutrino double-beta decay of ^{94, 96}Zr,^98,100Mo,¹⁰⁴Ru and ¹¹⁰Pd nuclei for the 0⁺0⁺ transition is studied in the PHFB model in conjunction with the summation method. In the first step, the reliability of the intrinsic wave functions has been established by obtaining an overall agreement between a number of theoretically calculated spectroscopic properties and the available experimental data for ^{94, 96}Zr,^94,96,98,100Mo, ^98,100,104Ru, ^104,110Pd and ¹¹⁰Cd isotopes. Subsequently, the PHFB wave functions of the above-mentioned nuclei are employed to calculate the nuclear transition matrix elements M₂ as well as half-lives T_1/2². Furthermore, we have studied the effects of deformation on the M₂.     

A novel method for determining the single particle potential directly from the measured single particle density: Application to the charge density difference between the isotones <Superscript>206</Superscript>Pb–<Superscript>205</Superscript>Tl

We present a novel method, based on the single particle Schroedinger equation, to determine the central potential (mean-field) directly from the single particle matter density and its first and second derivatives. As an example, we consider the experimental data for the charge density difference between the isotones ²⁰⁶Pb–²⁰⁵Tl, deduced by phase shift analysis of elastic electron scattering cross-section measurements and corresponds to the shell model 3s_1/2 proton orbit, and determine the corresponding single particle potential. We also present results of least-square fits to parametrized single particle potentials. The 3s_1/2 wave functions of the determined potentials reproduce fairly well the experimental data within the quoted errors. More accurate experimental data, with uncertainty smaller by a factor of two or more, may answer the question how well can the data be reproduced by a calculated 3s_1/2 wave function.     

Total reaction cross sections measurement for <Superscript>6,8</Superscript>He and <Superscript>8,9</Superscript>Li nuclei with energies of (25–45)/<Emphasis Type="Italic">A</Emphasis> MeV on <Superscript>nat</Superscript>Al and <Superscript>nat</Superscript>Pb

Preliminary results of measurements of the total reaction cross sections σ_R for weakly-bound ^6,8He and ^8,9Li nuclei at energy range (25–45)/A MeV on ²⁷Al and ²⁰⁸Pb targets are presented. The secondary beams of ^6,8He and ^8,9Li were produced by bombardment of the ¹¹B (33 A MeV) primary beam on Be (89 mg cm^–2) target and separated by COMBAS fragment-separator. In dispersive focal plane a horizontal slit defined the momentum acceptance as 1% and a wedge degrader of 200 μm Al was installed. The B_ρ of the second section of the fragment-separator was adjusted for measurements in energy range (25–45)/A MeV. The secondary products were detected by a telescope consisting of two Si ΔE detectors 300, 1000 μm and E-detector, which consisted of nine CsI/Tl granules.     

Process of negative-muon-induced formation of an ionized acceptor center (<Subscript>μ</Subscript>A)<Superscript>–</Superscript> in crystals with the diamond structure

A new subtractive procedure for canceling ultraviolet and infrared divergences in the Feynman integrals described here is developed for calculating QED corrections to the electron anomalous magnetic moment. The procedure formulated in the form of a forest expression with linear operators applied to Feynman amplitudes of UV-diverging subgraphs makes it possible to represent the contribution of each Feynman graph containing only electron and photon propagators in the form of a converging integral with respect to Feynman parameters. The application of the developed method for numerical calculation of two- and threeloop contributions is described.     

Geometric Phase in a Time-Dependent System with <Emphasis Type="Italic">ℑ</Emphasis><Superscript>(Ω)</Superscript> Algebra Structure

By using of the invariant theory, we have studied the geometric phase in a time-dependent system with ℑ ^(Ω) algebra structure, the dynamical and geometric phases are given, respectively. The Aharonov-Anandan phase is also obtained under the cyclical evolution. The disappearing condition of the geometric phase is given.