Rotational transitions in degenerate vibrational states of C3v symmetric top molecules,with application to CH3C15N

General algebraic expressions for the vibration-rotation energy levels and the associated rotational transitions of C_3v symmetric top molecules are developed. These expressions are presented in a convenient form for analysing the spectra of a molecule with any degree of excitation of a degenerate vibrational mode and have been applied to the spectrum of CH₃C¹⁵N.     

Difference of total cross sections for π± on 9Be and the π-9Be effective coupling constant

We have performed an extrapolation below 100 MeV of the difference in the total cross sections for π^± on ⁹Be by means of an optical potential. This low energy region gives a non-negligible contribution to the π-⁹Be effective coupling constant.     

An energy law preserving C finite element scheme for simulating the kinematic effects in liquid crystal dynamics

In this paper, we use finite element methods to simulate the hydrodynamical systems governing the motions of nematic liquid crystals in a bounded domain Ω. We reformulate the original model in the weak form which is consistent with the continuous dissipative energy law for the flow and director fields in W^1,2+σ(Ω) (σ > 0 is an arbitrarily small number). This enables us to use convenient conformal C⁰ finite elements in solving the problem. Moreover, a discrete energy law is derived for a modified midpoint time discretization scheme. A fixed iterative method is used to solve the resulted nonlinear system so that a matrix free time evolution may be achieved and velocity and director variables may be solved separately. A number of hydrodynamical liquid crystal examples are computed to demonstrate the effects of the parameters and the performance of the method.     

Microscopic optical model analysis of elastic scattering cross sections for nucleon-40Ca systems at low energy

Neutron and proton-⁴⁰Ca elastic scattering angular distributions and total reaction cross sections are calculated between 10 and 40 MeV using the microscopic optical potential derived by Bouyssy et al. within the nuclear structure approach. Direct comparison with experiment confirms that our calculation reproduces the imaginary potential at low energy for protons, but it gives insufficient absorption above the deuteron pick-up threshold. A renormalization of both the real and the imaginary parts of the potential leads to good agreement with the data. For both parts of the potential this renormalization is compatible with the renormalization factors obtained by Bouyssy et al. from a comparison of calculated and phenomenological volume integrals.     

Pomeron dominance in a triple-Regge representation of inclusive Δ++ production in K−p and π−p reactions

Data are presented on the reactions K^?p → Δ⁺⁺ + anything at 10 and 16 GeV/c and π^?p → Δ⁺⁺ + anything at 16 GeV/c. In the K^?p reaction, scaling is observed between 10 and 16 GeV/c in the variable M²/s. The scaling occurs at relatively low values of M in marked contrast to the reaction π⁺p → Δ⁺⁺ + anything. This result can be explained by duality arguments on a triple Regge picture, since the exchanged reggeon-incident particle scattering is exotic. Comparison of the π^?p reaction, which is similarly exotic, with the K^?p reaction at the same energy gives further evidence for factorization in pomeron-dominated inclusive reactions.     

Effective medium theory for the inhomogeneous PdMnxFe1−x alloys

Ternary PdMn_xFe_1−x alloys are known to form a microinhomogeneous random mixture of PdMn and PdFe phases. The unconventional ρ(x) dependence of dc resistivity and singularities in low frequency optical conductivity spectra of alloys are described footing within the effective medium approach. The essential point of the model proposed is the anomalous role of insulating interfaces, whose proliferation at intermediate x gives rise to the observed maximum of resistivity near x?0.8.     

A measurement of the KL0p elastic cross section for 3 ⩽p⩽13 GeV/c and 0.1⩽|t|⩽1.3 GeV2

The cross section for the K_L⁰p elastic scattering has been measured for the first time. The incident momentum and momentum transfer ranges are 3 ?p? 13 GeV/c, 0.1 ? |t| ? 1.3 GeV². The results are compared to those of other experiments related to ours by isotopic spin conservation, finding agreement with some and discrepancies with others. The differential cross sections have been parametrized in the form Ae^bt. The coefficients show little or no dependence on energy, with A ? 9.8 mb · GeV^?2and b ? 4.7 GeV^?2. The effective linear trajectory has been determined and gives α₀ = 0.95 ± 0.15, α′ = ?0.35 ± 0.48 GeV^?2, in good agreement with dominance by pomeron exchange.     

Analysis of the11B(p, γ0)12C reaction in terms of the direct and direct-semidirect capture models

The experimental data for 11B(p,γ₀)¹²C reaction in the proton energy range of 0.5–14 MeV were analysed within the conventional direct-semidirect capture model as well as within the modified approach of pure direct nucleon capture in the energy dependent effective nuclear field. The modified approach was found to provide a convenient tool for describing the reaction data in a broad energy range.     

Failsafe flux limiting and constrained data projections for equations of gas dynamics

A new approach to flux limiting for systems of conservation laws is presented. The Galerkin finite element discretization/L² projection is equipped with a failsafe mechanism that prevents the birth and growth of spurious local extrema. Within the framework of a synchronized flux-corrected transport (FCT) algorithm, the velocity and pressure fields are constrained using node-by-node transformations from the conservative to the primitive variables. An additional correction step is included to ensure that all the quantities of interest (density, velocity, pressure) are bounded by the physically admissible low-order values. The result is a conservative and bounded scheme with low numerical diffusion. The new failsafe FCT limiter is integrated into a high-resolution finite element scheme for the Euler equations of gas dynamics. Also, bounded L² projection operators for conservative interpolation/initialization are designed. The performance of the proposed limiting strategy and the need for a posteriori control of flux-corrected solutions are illustrated by numerical examples.     

Asymmetric chiral colour

Chiral colour is considered in a general framework where the coupling constants associated with eachSU(3) component are allowed to be different. To reproduce QCD at low energy, gluons and axigluons cannot then be maximally mixed. Present data frome ⁺ e ^? colliders constrains the axigluon mass to values between 50 GeV and 375 GeV whilst the mixing angle is bounded by 13° and 45°. The lower limit of the axigluon mass is a definite bound at 90% C.L., whereas the upper limit only applies if chiral colour is to explain the anomalously high rates of hadron production at TRISTAN.     

Microscopic study of the 12C + 16O system

An angular momentum projected microscopic calculation is performed for the ¹²C + ¹⁶O system with an effective nuclear force and the exact Coulomb interaction. The ¹²C wave function is projected on a 0⁺ state. Parametrizations of the Coulomb interaction between the nuclei are fitted. The L-projected energy curves present a quite complicated structure especially for the negative parity states. The role played by critical angular momenta is put into evidence. A generator coordinate calculation gives several bands of bound, quasibound and virtual states. Excellent agreement in energy and angular momentum is obtained with the 13.7 MeV (J = 9), 19.7 MeV (J = 14), 22.7 MeV (J = 15) and other resonances.     

Eigenvalues, eigenfunctions, and surface states in finite periodic systems

Using a simple approach that requires neither the Bloch functions nor the reciprocal lattice, new, compact, and rigorous analytical formulas are derived for an accurate evaluation of resonant energies, resonant states, energy eigenvalues and eigenfunctions of open and bounded n-cell periodic systems with arbitrary 1D potential shapes, provided the single cell transfer matrix is given. These formulas are applied to obtain the energy spectra and wave functions of a number of simple but representative open and bounded superlattices. We solve the fine structure in bands and exhibit unambiguously that the true eigenfunctions do no not fulfill the periodicity property |Ψ_μ,ν (z + l_c)|² = |Ψ_μ,ν (z)|², with l_c the single cell length. We show that the well known surface states and surface energy levels come out naturally. We analyze the surface repulsion effect and calculate exactly the surface energy levels for different potential discontinuities an the ends.     

Velocity dependence of the chemi-ionization of H2O and D2O on impact of 21S and 23S helium atoms

The velocity dependence for the ionization of H₂O and D₂O to form H₂O⁺ and D₂O⁺ in collisions with both 2³S and 2¹S metastable helium atoms has been measured in a crossed molecular beam apparatus using a mechanical velocity-selector on the metastable beam. The cross-sections are found to be proportional to the —n power of the relative collision energy, with n ? 0.4 for both metastable atoms in both gases. The branching ratios H₂O⁺/OH⁺ and D₂O⁺/OD⁺ were both found to be 4.3 for both metastable helium atoms, and to be independent of the relative collision energy.     

The compound nucleus reaction 12C(11B, 2α) 15N

Energy spectra and differential cross sections of nitrogen products formed in the reaction 28 MeV ¹¹B + ¹²C have been measured using a ΔE?E counter telescope. The energy spectra are smooth and therefore indicate that the nitrogen products were formed by a compound nucleus mechanism, via the formation and decay of the compound nucleus ²³Na. The experimental results are compared with statistical model calculations and good agreement is obtained. This result provides further evidence for the importance of the compound nucleus mechanism in heavy ion reactions with light nuclei and also gives added validity to the statistical model for light compound systems.     

Elastic scattering of vector polarized deuterons by 4He

The vector analyzing power iT₁₁ for deuterons elastically scattered by ⁴He has been measured for c.m. angles between 51.8° and 158.9° and deuteron energies in the range 11.5 to 17 MeV. The results show that d-α scattering is a convenient analyzer for deuteron vector polarization in the energy range investigated, since the angular dependence of iT₁₁ is fairly insensitive to energy and the magnitude of iT₁₁ is quite large at some angles.     

Exact four-body calculation of the 4ΛHe-4ΛH binding energy difference

The coupled, two-variable integral equations that determine the ⁴_ΛHe and ⁴_ΛH bound states, when the NN and ΛN interactions are represented by separable potentials, are derived from the Schrödinger equation. The integral equations are solved numerically for simple s-wave potentials and for tensor potentials in the truncated t-matrix approximation without resort to separable expansion of the kernels. The Λ-separation energy difference ΔB_Λ resulting from the genuine four-body model is shown to be approximately twice as large as that coming from an “effective two-body” model calculation, when identical central potentials are used. The four-body model estimate of ΔB_Λ made with tensor forces is consistent with the experimental value, indicating that charge symmetry breaking implied by the low energy Λ N scattering parameters is compatible with that suggested by the known binding energy difference in the A = 4 hypernuclear isodoublet.