Mechanisms of formation of P-odd,P-even and T-odd asymmetries in the angular distributions of products of binary and ternary fission induced by cold polarized neutrons

The experimentally measured P-odd, T-even; P-even, T-even; and P-even, T-odd asymmetries in the angular distributions of products of binary and ternary fission induced by cold polarized neutrons are classified, and the mechanisms of their appearance are studied. Basic asymmetries in the angular distributions of binary-fission fragments are found theoretically and are used to construct induced asymmetries in the angular distributions of prescission and evaporated third particles emitted in true and delayed ternary fission. If effects associated with the collective rotation of the polarized fissile system are disregarded, P-odd, T-even; P-even, T-even; and P-even, T-odd asymmetries in the angular distributions of prescission and evaporated photons are proven to be absent, and the coefficients of the analogous asymmetries in the angular distributions of prescission and evaporated neutrons are calculated for this case. The features of the coefficients of induced P-even, T-odd asymmetries are studied for evaporated photons and neutrons associated with taking into account the quantum rotation of the polarized fissile system.     

Reformulation of general relativity as a gauge theory

The starting point is a spinor affine space-time. At each point, two-component spinors and a basis in spinor space, called “spin frame,” are introduced. Spinor affine connections are assumed to exist, but their values need not be known. A metric tensor is not introduced. Global and local gauge transformations of spin frames are defined with GL(2) as the gauge group. Gauge potentials B_μ are introduced and corresponding fields F_μν are defined in analogy with the Yang-Mills case. Gravitational field equations are derived from an action principle. Incases of physical interest SL(2, C) is taken as the gauge group, instead of GL(2). In the special case of metric space-times the theory is identical with general relativity in the Newman-Penrose formalism. Linear combinations of B_μ are generalized spin coefficients, and linear combinations of F_μν are generalized Weyl and Ricci tensors and Ricci scalar. The present approach is compared with other formulations of gravitation as a gauge field.     

Two-photon excitation and ionization of inner atomic shells

The spectrum of platinum is studied in the region from 250 to 1250 Å. The twenty-two 5d6s-5d6p spectral lines of the PtIX are assigned. All levels of the 5d6s configuration are found. The assignment of the previously known 5d6p levels is confirmed and their positions are refined. The 5d ², 5d6s, and 5d6p configurations are theoretically described by the method of orthogonal operators. These calculations are compared with the data obtained by a conventional method using the Cowan program.     

Raman spectra of GaAs-AlxGa1-xAs superlattices

Systematic theoretical studies of Raman spectra of GaAs-Al_xGa_1-xAs superlattices are presented. The electronic states are described by an envelope-function method and the phonon modes are described in a microscopic rigid-ion model. Both resonant and nonresonant Raman scattering processes are considered. For resonant Raman scattering, the effects of discrete exciton states plus the continuum and the valence-band mixing are included via a k-space sampling method. Both the Fröhlich and deformation-potential mechanisms for electron-phonon coupling are considered. These two mechanisms are responsible for principal features in the z(x, x)z̄ and z(x, y)z̄ geometries, respectively. We find that the effects of exciton continuum states are quite important and the resonant Raman spectra so obtained are in much better agreement with experiment compared to those without including the exciton continuum states.     

Proton, deuteron, and triton emission in 14N+Ag interactions at an energy of 52 MeV per nucleon

The inclusive energy spectra and multiplicities of p, d, and t from the reactions ¹⁴N(Ag, X), X=p, d, t at E/A=52 MeV are measured. The experimental data are compared with the results obtained within the Dubna version of the cascade model and are analyzed on the basis of the moving-source model.     

Departures from the Hauser-Feshbach theory due to the level-level correlations in deformed nuclei

A microscopic dynamical model is used for the inelastic scattering of nucleons by deformed nuclei and the fluctuation cross sections are calculated. The case of weak absorption in all channels is considered so that the number of statistical assumptions is minimized. The results are compared with the Hauser-Feshbach expressions as regards the magnitude and structure. The partial width amplitudes calculated from the model are correlated, the simplest type of level-level correlations being due to the similar-channels effect (SCE). When the correlations are due to SCE alone, the following two results are obtained, (i) The fluctuation cross sections are increased over the Hauser-Feshbach estimates, for Γ ? D and Γ ? D, by a factor κ if the entrance and exit channels are similar. The numerical value of κ is found to be 3 for a special case and in the general case it is conjectured to lie between the limits 1 and 3, (ii) The fluctuation cross sections σ_cc′^f1 and σ^f1_cc″ exhibit correlated fluctuations if the exit channels c′ and c″ are similar. The fluctuation cross sections in the cases “SCE+direct channel-channel coupling” and “SCE+intermediate structure” are also investigated. In all cases studied direct reaction cross sections do not vanish and the channelwise factorization assumption of the Hauser-Feshbach theory fails.     

Electromagnetic corrections to masses and widths in the baryon decuplet,and to π± d cross section at the Δ resonance

The electromagnetic mass splittings of theΔ andγ members of the decuplet are estimated and the resulting decay widths are calculated, assumingSU(2)-invariance of the coupling constants for “unmixed” states. Three additional Coulomb corrections occur when deuterons are used as neutron targets. The combined effects onπ ^± d total cross sections are given.     

Vibrational spectra of Matrix isolated binary and mixed cadmium dihalides

The Raman spectra CdX₂ and CdXY (X, Y = Cl, Br, I) molecules isolated in solid krypton at 20°K are reported together with the matrix isolation infrared spectrum of CdX₂ and CdXY (X, Y = Br, I) molecules. Isotopic effects and force constants are discussed and several irregularities in them are interpreted as possible indications of slightly bent structures. The bending vibration frequency of CdClI as well as several bands assigned to dimers are also reported.     

Z-dependences of atomic characteristics of ions in Be- and O-isoelectronic sequences (2s−2p transition)

Transition energies and probabilities are presented for ions of the Be(Z = 4?100) and O(Z = 8?100) isoelectronic sequences. Dipole transitions are considered between all low-lying states constructed from 2s², 2s2p, and 2p² configuration in the case of Be-like ions, and between all low lying states from 2s²2p⁴, 2s2p⁵, and 2p⁶ configurations in the case of O-like ions. The calculations are based on the $\text{1}\text{Z}$ expansion technique and are carried out in the intermediate coupling scheme. Relativistic effects are incorporated using the Breit operator. For Z > 40, it is shown that jj-coupling is applicable. Results of the present calculations are compared with those of other authors over a broad range of nuclear charges.     

Some characteristic behavior of mixed spin-1/2 and spin-1 Ising nano-tube

The magnetization of a cylindrical Ising nano-tube is investigated by the use of the effective field theory with correlations. The effects of the crystal field couplings at the surface shell to the order parameters, susceptibility, internal energy, specific heat and free energy are investigated. Some characteristic phenomena are examined in the thermal variations, depending on crystal field term. Moreover, tricritical and critical points are found on the (D/J,kT/J) plane, where D/J and kT/J are reduced crystal-field and temperature, respectively.     

Dynamic phase transitions in the kinetic spin-1 Blume-Capel model on the Bethe lattice

The stationary states of the kinetic spin-1 Blume-Capel (BC) model on the Bethe lattice are analyzed in detail in terms of recursion relations. The model is described using a Glauber-type stochastic dynamics in the presence of a time-dependent oscillating external magnetic field (h) and crystal field (D) interactions. The dynamic order parameter, the hysteresis loop area and the dynamic correlation are calculated. It is found that the magnetization oscillates around nonzero values at low temperatures (T) for the ferromagnetic (F) phase while it only oscillates around zero values at high temperatures for the paramagnetic (P) phase. There are regions of the phase space where the two solutions coexist. The dynamic phase diagrams are obtained on the (kT/J,h/J) and (kT/J,D/J) planes for the coordination number q=4. In addition to second-order and first-order phase transitions, dynamical tricritical points and triple points are also observed.     

Dependence of calculated collective nuclear properties on the form of the potential energy and inertia tensor

A systematic study of the dependence of the collective quantities (energies and matrix elements of the E2, M1 and E0 moments) on the form of approximations to the potential energy V and the inertia tensor B is performed. Various approximations used up to now are tested. Macroscopic-microscopic values for V and cranking results for B are taken as a reference. The collective quantities are calculated by solving the Schrödinger equation corresponding to the collective Bohr hamiltonian. The contribution of all nucleons is explicitly taken into account; no renormalization factors are used. Spherical, transitional and deformed even-even nuclei are considered. The quality of various approximations for V and B used in the boson-expansion method is discussed. Large effects of the microstructure of the inertia tensor B are obtained and commented on.     

Numerical computation of an important integral function in two-dimensional radiative transfer

Analytical properties, series expansions and asymptotic expansions are generated for S_n(x) which are important integral functions in the analysis of two-dimensional radiative transfer. These functions are shown to be Fourier transform of the generalized exponential integral function. Table of values of S₁(x), S₂(x), and S₃(x) are presented.     

The pair distribution function of moderately dense quantum fluids

The density expansion for the pair distribution functiong(r) and the structure factorS(k) for interacting quantum systems are given. These functions are thus represented by means of theT-matrices of the two-, three-,... body scattering problem. Possibly existing bound states are taken into account. Explicit expressions for the quantum virial coefficients in terms ofg(r) or ofT-matrices are derived.     

Exact boson mappings for nuclear neutron (proton) shell-model algebras having SU(3) subalgebras

In this paper the commutation relations of the fermion pair operators of identical nucleons coupled to spin zero are given for the general nuclear major shell in LST coupling. The associated Lie algebras are the unitary symplectic algebras Sp(2M). The corresponding multipole subalgebras are the unitary algebras U(M), which possess SU(3) subalgebras. Number conserving exact boson mappings of both the Dyson and hermitian form are given for the nuclear neutron (proton) s−d, p−f, s−d−g, and p−f−h shells, and their group theoretical structure is emphasized. The results are directly applicable in the case of the s−d shell, while in higher shells the experimentally plausible pseudo-SU(3) symmetry makes them applicable. The final purpose of this work is to provide a link between the shell model and the Interacting Boson Model (IBM) in the deformed limit. As already implied in the work of Draayer and Hecht, it is difficult to associate the boson model developed here with the conventional IBM model. The differences between the two approaches (due mainly to the effects of the Pauli principle) as well as their physical implications are extensively discussed.     

The crystal-field dependency of sound attenuation in the spin-3/2 ising model

The effects of crystal-field (D) on sound attenuation are considered for the spin-3/2 Ising model by using Onsager theory of irreversible thermodynamics. It is assumed that the sound wave couples to the order-parameter fluctuations, therefore, it decays mainly via order-parameter relaxation process. The order-parameters, magnetization and quadrupole moment, are defined in terms of exact recursion relations (ERR) on Bethe lattice (BL). After our analysis, two relaxation times are obtained and they are used to calculate the sound attenuation coefficient (α). Consequently, the critical behaviors of sound attenuation coefficient are investigated in terms of frequency (w) and Onsager coefficient (γ) for the coordination numbers q=3, 4 ad 6 near the second-order (T_c) and first-order (T_t) phase transition temperatures in the ferromagnetic phase regions for the negative and positive D values and the results are presented on the (k_BT/J, α) planes. It is found that the peaks about T_t’s are observed at the same temperature, but the peaks about T_c’s are observed shifted to lower and higher temperatures in increasing (w)’s and (γ)’s, respectively. In addition, the peaks are also obtained near the tricritical points for all q.     

On the zero points of the mandelstam denominators in the complexs-plane: The general two-body process

The relativistic two-body into two-body processes are considered. The areas are described where the denominators of the Mandelstam representation vanish in the complexs-plane if the momentum transfer squaredt and the scattering angle? in the direct channel have physical values. The equations of the lines are given along which either cos?=const andt varies ort=const and cos? varies. The cuts along later lines are suggested if the continua in the crossed channels are replaced by particles. In the general mass case, it is shown that the location of the branch points in the integrand of the partial wave amplitude in the complexs-plane depends on the integration involved. However, any elastic process represents a degeneration when the mentioned dependence does not appear.     

Electronic spectra of XeNe molecules in the range 77100-90100 cm-1 near Xe* (6p, 5d, 6p’, 7s, 7p, 6d) obtained by the (3 + 1) REMPI and (2 + 1) REMPI methods

The electronic spectra of XeNe molecules in the range of 77100-90100 cm^-1 are measured by the method of laser resonance multiphoton ionization in a supersonic jet. The photoionization spectra are obtained upon two- and three-photon excitations of molecules and their ionization by the next photon. In the range of 80300-90100 cm^-1 near Xe*(5d, 6p’, 6d, 7s, and 7p), the spectra are obtained for the first time. A whole number of vibrational systems are measured in this range. The majority of vibrational systems near Xe* (5d, 6d, 7p, and 7s) are located in the red range with respect to their dissociation limits. In the blue range with respect to the dissociation limits, continua corresponding to transitions of molecules from the ground state to repulsive potential curves of excited states are detected. For a number of excited states of XeNe molecules, the vibrational analysis is performed and molecular constants are estimated.     

Two-dimensional radiative equilibrium: Boundary emissive powers for a finite medium subjected to cosine varying radiation

Exact expressions are presented for the emissive power at the boundaries of a two- dimensional, finite, planar, absorbing-emitting, gray medium exposed on one side to cosine varying radiation and on the other side to no radiation. The emissive powers at the boundaries of a medium illuminated by cosine varying collimated radiation are the generalized X- and Y-functions which are analogous to Chandrasekhar's X- and Y-functions. Integro-differential equations for the generalized X- and Y-functions are formulated and reduced to a system of ordinary differential equations and are solved numerically. The emissive powers at the boundaries for cosine varying diffuse radiation are moments of the generalized X- and Y-functions.