Single photo and electroproduction of pions at EBAC@JLAB

Within the Excited Baryon Analysis Center we have performed a dynamical coupled-channels analysis of the available p(e,e'π)N data in the region of W ≤ 1.6 GeV and Q~2≤ 1.45 (GeV/c)~2. The channels included are γN, πN, ηN, and ππN which has π△, ρN, and σN components. With the hadronic parameters of the model determined in our previous investigations of πN→πN reaction, we have found that the available data in the considered W≤1.6 GeV region can be fitted well by only adjusting the bare γ~*N→N~* helicity amplitudes for the lowest N~* states in P_(33), P_(11), S_(11) and D_(13) partial waves. The meson cloud effect, as required by the unitarity conditions, on the γ~*N→ N~* form factors are examined.     

The structure and lattice dynamics of RbBr(1 0 0) and RbI(1 0 0) single crystal surfaces: A tensor low energy electron diffraction analysis

The structure and lattice dynamics of RbBr(1 0 0) and RbI(1 0 0) single crystal surfaces cleaved under UHV conditions were investigated by means of low energy electron diffraction (LEED) at temperatures of 156 K and 183 K, respectively. Since RbBr and RbI are insulators the experiments were carried out with a microchannel plate LEED system at very low primary currents (5 nA). For both materials four different diffraction orders could be observed. Diffraction patterns were recorded over an energy range from 30 eV to 220 eV in increments of 2 eV and I(V) curves for each spot were extracted. The I(V) curves were analyzed using the tensor LEED approach. For both alkali halide substrates surface structures of (1 × 1) periodicity close to the truncated bulk structure were found. For RbBr, the first interlayer distance is reduced by about 2.2%, where the Rb⁺ cations in the topmost layer are shifted inwards by 0.06(3) Å, and the anions also exhibit an inward shift which is however smaller (0.04(3) Å). The root mean square vibrational amplitudes are enlarged by a factor of 1.3 for Rb⁺ and 1.25 for Br⁻, respectively. For RbI(1 0 0) the cations of the topmost layer are shifted inwards by 0.07(3) Å and the anions outwards by 0.02(1) Å. The vibrational amplitudes of the ions are not enlarged as for RbBr but close to the corresponding bulk values.     

圆弧形沉积场地对平面瑞利波散射的解析分析

分别采用Biot饱和多孔介质动力学理论和单相介质弹性动力学理论模拟层状沉积谷场地和 周围场地,利用波函数展开法,得出了层状饱和沉积场地对Rayleigh波散射的解析解．进 行参量分析,研究了无量纲入射波频率、层状沉积层排列顺序及相对刚度和厚度等因素对 Rayleigh波散射效应的影响.     

Phase shift analysis ofππ scattering

A novel approach to energy dependent phase shift analysis ofππ scattering is proposed. Optimised polynomial expansions of Roskies’ amplitudes are given. The parameters of these expansions are searched out by making a fit to the differential cross-sections. Then the transformation matrix between Roskies’ amplitudes and the conventional partial waves is used to compute the phase shifts and inelasticities. Significant improvement is observed in so far as the number of free parameters for a fixed energy phase shift analysis is concerned. Value for the effective Chew-Mandelstam coupling constant, λ_CM, is also estimated.     

Valence bond corrected single reference coupled cluster approach

Summary An extension of the single reference coupled cluster method truncated to 1- and 2-body cluster components (CCSD) to quasidegenerate systems, where 3-and 4-body connected cluster components play an important role, is proposed. The basic idea is to extract the information concerning the 3- and 4-body clusters from some independent source, similarly as was implicitly done in the so-called ACPQ or ACC(S)D methods, and correct accordingly the absolute term in the CCSD equations. As a source of these approximate 3- and 4-body clusters, simple valence bond (VB) type wave functions are employed, since they are capable of describing electronic structure of various molecular systems for a wide range of nuclear conformations including their dissociation. The cluster analysis of these VB wave functions, that provides the desired information concerning the connected 3- and 4-body cluster components, is outlined and the explicit form of required correction terms to the CCSD equations is given.     

Mittlere Schwingungsamplituden von HBCl2, HAlCl2 und HGaCl2

Summary Mean amplitudes of vibration of the isostructural molecules HBCl₂, HAlCl₂ and HGaCl₂ and of its deuterated analogous have been calculated from spectroscopic data in a wide temperature range. The results are briefly discussed and some comparisons with data of related species are also made.

     

Mean amplitudes of vibration for PMo12O40 3− and its fragments

Mean amplitudes of vibration () are calculated for all 80 distance types in PMo₁₂O₄₀ ^3–. The values are discussed and some of them compared with the corresponding values calculated for, five different fragments of the structure. Reasonable values (<0.12 Å at 298 K) are found even for extremely long distances, e.g. 0.078 Å at 298 K for the longest oxygen-oxygen distance (10.4 Å). The values for bonded distances as well as a number of nonbonded distances have comparable magnitudes in the fragments and the whole structure; in other cases the fragment values are substantially higher.

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Mittlere Schwingungsamplituden für PMo₁₂O₄₀ ^3– und Fragmente

Zusammenfassung Mittlere Schwingungsamplituden () für alle 80 Typen von Abständen in PMo₁₂O₄₀ ^3– wurden berechnet. Die Werte werden diskutiert und einige werden mit denen von fünf verschiedenen Fragmenten der untersuchten Struktur verglichen. Es wurden auch für extrem große Distanzen plausible -Werte (<0,12 Å bei 298 K) gefunden (z. B. 0,078 Å bei 298 K für die größte, O–O-Distanz 10,4 Å). Die, -Werte für Bindungslängen und auch für einige Abstände von nicht aneinander gebundenen Atomen weisen in den Fragmenten und in der Gesamtstruktur vergleichbare Größe auf; in anderen Fällen sind die Fragment-Werte allerdings bedeutend höher.

     

Isotopic invariants of pyramidal symmetrical XY3 molecules and evaluation of molecular constants

The isotopic invariants of pyramidal symmetrical XY₃ molecules are calculated in terms of frequencies, Coriolis coupling constants, molecular geometry parameters and masses of the constituent atoms. These invariants are used to evaluate force constants, compliance constants and mean amplitudes of vibration of four sets of 12 isotopic molecules.     

Violation of the Okubo-Zweig-Iizuka rule in the decay mode B(1235) →φ(1020) +π

The Okubo-Zweig-Iizuka rule forbids the transitionB(1235)→φπ. Unitarity, however, induces a non-vanishing amplitude forB→φπ. We estimate the amplitude using dispersion relation. The absorptive part is shown to be small contributing less than 100 keV to the partial width Γ (B→φπ). For the dispersive part we evaluate the contributions of the and intermediate states and point out that the state does not contribute significantly. The dispersive part contributes about 300 keV to the partial width. Thus unitarity correction to the Okubo-Zweig-Iizuka rule gives the partial width Γ(B→φπ) to be around 300–400 keV compared with the present experimental upper limit of 1·9 MeV.