J an 2 00 6 Configuration Interaction calculations of positron binding to Be ( 3 P o )
The Configuration Interaction method is applied to investigate the possibility of positron binding to the metastable beryllium (1s22s2p 3Po) state. The largest calculation obtained an estimated energy that was unstable by 0.00014 Hartree with respect to the Ps + Be+(2s) lowest dissociation channel. It is likely that positron binding to parent states with non-zero angular momentum is inhibited by centrifugal barriers.
Convergence of the Partial Wave Expansion of the He Ground State
The configuration interaction (Cl) method, using a very large Laguerre orbital basis, is applied to the calculation of the He ground state. The largest calculations included a minimum of 35 radial orbitals for each l ranging from 0 to 12, resulting in basis sets in excess of 400 orbitals. The convergence of the energy and electron-electron delta-function with respect to J (the maximum angular momenta of the orbitals included in the CI expansion) were investigated in detail. Extrapolations to the limit of infinite angular momentum using expansions of the type Delta X-J = A(X)[J + 1/2](-p) + B-X[J + 1/2](-mu-1) +..., gave an energy accurate to 10(-7) Hartree and a value of accurate to about 0.5%. Improved estimates of and , accurate to 10(-8) Hartree and 0.01%, respectively, were obtained when extrapolations to an infinite radial basis were done prior to the determination of the J -> infinity limit. Round-off errors were the main impediment to achieving even higher precision, since determination of the radial and angular limits required the manipulation of very small energy and differences.
Integrated two-beam antenna array featuring dual-circular polarization
A concept of an integrated antenna array featuring two independent beams and dual circular polarization has been described. The antenna array consists of two radiating elements which are excited at two orthogonally placed feeding ports with the use of four appropriately connected 3-dB/90° directional couplers. Therefore, such an array generates two symmetrically located beams having right-handed circular polarization (RHCP) and identical two beams having left-handed circular polarization (LHCP). The presented concept has been verified by the design and measurements of an antenna array operating at 2.4 GHz frequency range.