Isotope shift on the chlorine electron affinity revisited by an MCHF/CI approach

Today, the electron affinity is experimentally well known for most of the elements and is a useful guideline for developing ab initio computational methods. However, the measurements of isotope shifts on the electron affinity are limited by both resolution and sensitivity. In this context, theory eventually contributes to the knowledge and understanding of atomic structures, even though correlation plays a dominant role in negative ions properties and, particularly, in the calculation of the specific mass shift contribution. The present study solves the longstanding discrepancy between calculated and measured specific mass shifts on the electron affinity of chlorine (Phys. Rev. A 51 (1995) 231)Comment: 18 pages, 2 figures, 7 table

Atomic Parameters for the 2p53p 2[3/2]2−2p53s 2[3/2]2o2p^53p~^2[3/2]_2 - 2p^53s~^2[3/2]^o_2 Transition of Ne I relevant in nuclear physics

We calculated the magnetic dipole hyperfine interaction constants and the electric field gradients of $2p^53p~^2[3/2]_2$ and $2p^53s~^2[3/2]^o_2$ levels of Ne I by using the multiconfiguration Dirac-Hartree-Fock method. The electronic factors contributing to the isotope shifts were also estimated for the $\lambda = 614.5$ nm transition connecting these two states. Electron correlation and relativistic effects including the Breit interaction were investigated in details. Combining with recent measurements, we extracted the nuclear quadrupole moment values for $^{20}$Ne and $^{23}$Ne with a smaller uncertainty than the current available data. Isotope shifts in the $2p^53p~^2[3/2]_2 - 2p^53s~^2[3/2]^o_2$ transition based on the present calculated field- and mass-shift parameters are in good agreement with the experimental values. However, the field shifts in this transition are two or three orders of magnitude smaller than the mass shifts, making rather difficult to deduce changes in nuclear charge mean square radii. According to our theoretical predictions, we suggest to use instead transitions connecting levels arising from the $2p^53s$ configuration to the ground state, for which the normal mass shift and specific mass shift contributions counteract each other, producing relatively small mass shifts that are only one order of magnitude larger than relatively large field shifts, especially for the $2p^53s~^2[1/2]^o_1 - 2p^6~^1S_0$ transition

Accurate solution of the Dirac equation on Lagrange meshes

The Lagrange-mesh method is an approximate variational method taking the form of equations on a grid because of the use of a Gauss quadrature approximation. With a basis of Lagrange functions involving associated Laguerre polynomials related to the Gauss quadrature, the method is applied to the Dirac equation. The potential may possess a $1/r$ singularity. For hydrogenic atoms, numerically exact energies and wave functions are obtained with small numbers $n+1$ of mesh points, where $n$ is the principal quantum number. Numerically exact mean values of powers $-2$ to 3 of the radial coordinate $r$ can also be obtained with $n+2$ mesh points. For the Yukawa potential, a 15-digit agreement with benchmark energies of the literature is obtained with 50 mesh points or less

Core correlation effects in multiconfiguration calculations of isotope shifts in Mg I

The present work reports results from systematic multiconfiguration Dirac-Hartree-Fock calculations of isotope shifts for several well-known transitions in neutral magnesium. Relativistic normal and specific mass shift factors as well as the electronic probability density at the origin are calculated. Combining these electronic quantities with available nuclear data, energy and transition level shifts are determined for the $^{26}$Mg$-^{24}$Mg pair of isotopes. Different models for electron correlation are adopted. It is shown that although valence and core-valence models provide accurate values for the isotope shifts, the inclusion of core-core excitations in the computational strategy significantly improves the accuracy of the transition energies and normal mass shift factors.Comment: 2 figures, submitted to Physical Review

Theoretical isotope shifts in neutral barium

The present work deals with a set of problems in isotope shifts of neutral barium spectral lines. Some well known transitions ($6s^2~^1S_0-6s6p~^{1,3}P^o_1$ and $6s^2~^1S_0-6p^2~^3P_0$) are first investigated. Values of the changes in the nuclear mean-square charge radius are deduced from the available experimental isotope shifts using our ab initio electronic factors. The three sets $\{ \delta\langle r^2\rangle^{A,A'}\}$ obtained from these lines are consistent with each other. The combination of the available nuclear mean-square radii with our electronic factors for the $6s5d~^3D_{1,2} -6s6p~^{1}P^o_1$ transitions produces isotope shift values in conflict with the laser spectroscopy measurements of Dammalapati et al. (Eur. Phys. J. D 53, 1 (2009))

Atrypidae (Brachiopoda) de la Formation de Fromelennes (fin du Givetien) et de la partie inférieure de la Formation de Nismes (début du Frasnien) aux bords sud et sud-est du Synclinorium de Dinant (Belgique)

The authors describe the Atrypidae from the lower and upper (Fort Hulobiet Member) members of the Fromelennes Formation and from the lower part (Pont d'Avignon and Sourd d'Ave Members) of the Nismes Formation. Four species are new: Desquamatia (Independatrypa) coenaubertorum n. sp., D. (Seratrypa) orbiculata n. sp., D. (S?) suppinguis n. sp. and D. (Neatrypa) gosseleti n. sp.; two are assigned to D. (Seratrypa) pectinata COPPER. P., 1967 and D. (Neatrypa) europaea STRUVE. W., 1964. Rare or poorly preserved specimens are provisionally designated as D. (Seratrypa) cf. pectinata, D. (S.) sp. R, D. (Neatrypa) sp.S and Spinatrypina sp. The specimens have been collected for the most part from five outcrops located at the southern and south-eastern borders of the Dinant Synclinorium. The succession of the atrypid zones at the base of the Nismes Formation in these different outcrops shows, from south to north-east, the diachronism which has been already pointed out formerly, of the base of the unit

Using Partial Orders for the Efficient Verification of Deadlock Freedom and Safety Properties

This article presents an algorithm for detecting deadlocks in concurrent finite-state systems without incurring most of the state explosion due to the modeling of concurrency by interleaving. For systems that have a high level of concurrency, our algorithm can be much more efficient than the classical exploration of the whole state space. Finally, we show that our algorithm can also be used for verifying arbitrary safety properties

Le genre Paraspirifer Wedekind, R., 1926 dans le Dévonien moyen de la partie orientale de l’Amerique du Nord

The authors describe seven species of the genus Paraspirifer WEDEKIND, R., 1926 on the basis of more than one hundred specimens from twenty-three localities in North America. Three of these species are new: P. conradi n. sp., P. halli n. sp. and P. clarkei n. sp. Two others are provisionally named P. cf. halli and P. sp. A. A Neotype is proposed for P. acuminatus (CONRAD, T.A., 1839) and the Lectotype of P. brownockeri (STEWART, G.A., 1927) is designated. The problems concerning the species Terebratula acuminatissima DE CASTELNAU, F., 1843 and Delthyris prora CONRAD, T.A., 1842 are briefly discussed. The genus Paraspirifer is confined to an area of ± 6.500.000 km2 in eastern North America. In New York, the biostratigraphic range-zone for the genus is from the upper Onondaga Limestone (Moorehouse Member) to the middle Marcellus Shale (Solsville Member) and, in Ohio and Ontario, from the upper part of the Columbus Limestone (Zones F — H) to the Silica Shale. In Indiana and Kentucky, the genus occurs in the upper Jeffersonville Limestone (P. acuminatus sensu lato Zone) and, in Illinois and Missouri, in the Grand Tower Limestone