21,874 research outputs found
Variational separable expansion scheme for two-body Coulomb-scattering problems
We present a separable expansion approximation method for Coulomb-like
potentials which is based on Schwinger variational principle and uses
Coulomb-Sturmian functions as basis states. The new scheme provides faster
convergence with respect to our formerly used non-variational approach.Comment: some typos correcte
Electron-hydrogen scattering in Faddeev-Merkuriev integral equation approach
Electron-hydrogen scattering is studied in the Faddeev-Merkuriev integral
equation approach. The equations are solved by using the Coulomb-Sturmian
separable expansion technique. We present - and -wave scattering and
reactions cross sections up to the threshold.Comment: 2 eps figure
On the Coulomb-Sturmian matrix elements of the Coulomb Green's operator
The two-body Coulomb Hamiltonian, when calculated in Coulomb-Sturmian basis,
has an infinite symmetric tridiagonal form, also known as Jacobi matrix form.
This Jacobi matrix structure involves a continued fraction representation for
the inverse of the Green's matrix. The continued fraction can be transformed to
a ratio of two hypergeometric functions. From this result we find
an exact analytic formula for the matrix elements of the Green's operator of
the Coulomb Hamiltonian.Comment: 8 page
Three-potential formalism for the atomic three-body problem
Based on a three-potential formalism we propose mathematically well-behaved
Faddeev-type integral equations for the atomic three-body problem and descibe
their solutions in Coulomb-Sturmian space representation. Although the system
contains only long-range Coulomb interactions these equations allow us to reach
solution by approximating only some auxiliary short-range type potentials. We
outline the method for bound states and demonstrate its power in benchmark
calculations. We can report a fast convergence in angular momentum channels.Comment: considerably revised, 9 pages, revtex, 1 ps figur
First contribution to the knowledge of the braconid wasps (Hymenoptera, Braconidae) of Malta
A total of 48 species of braconid wasps (excluding 16 Aphidiidae) are
here reported as occurring in the Maltese Islands, of which 38 species are reported
for the first time from this territory. The braconid species of Malta belong to 13
subfamilies, of which two are the richest in terms of species diversity: Braconinae
with 10 and Microgastrinae with 16 species. One Microgastrinae, Dolichogenidea
zerafai sp. n. is described and distinguished from closely related species. The
majority of the known species are widely distributed in Europe or in the Palaearctic.
The braconid material is deposited in D. Mifsud’s private collection, with a few
duplicates in the Hungarian Natural History Museum, Budapest.peer-reviewe
Faddeev-Merkuriev equations for resonances in three-body Coulombic systems
We reconsider the homogeneous Faddeev-Merkuriev integral equations for
three-body Coulombic systems with attractive Coulomb interactions and point out
that the resonant solutions are contaminated with spurious resonances. The
spurious solutions are related to the splitting of the attractive Coulomb
potential into short- and long-range parts, which is inherent in the approach,
but arbitrary to some extent. By varying the parameters of the splitting the
spurious solutions can easily be ruled out. We solve the integral equations by
using the Coulomb-Sturmian separable expansion approach. This solution method
provides an exact description of the threshold phenomena. We have found several
new S-wave resonances in the e- e+ e- system in the vicinity of thresholds.Comment: LaTeX with elsart.sty 13 pages, 5 figure
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