Configuration-interaction calculations of positron binding to zinc and cadmium

Abstract

The configuration-interaction method is applied to the study of positronic zinc (e ϩ Zn) and positronic cadmium (e ϩ Cd). The estimated binding energies and annihilation rates were 0.003 73 hartree and 0.42ϫ10 9 sec Ϫ1 for e ϩ Zn and 0.006 10 hartree and 0.56ϫ10 9 sec Ϫ1 for e ϩ Cd. The low-energy elastic cross section and Z eff were estimated from a model potential that was tuned to the binding energies and annihilation rates. Since the scattering lengths were positive (14.5a 0 for Zn and 11.6a 0 for Cd͒ the differential cross sections are larger at backward angles than at forward angles just above threshold. The possibilities of measuring differential cross sections to confirm positron binding to these atoms is discussed.

Long-range interactions of excited He atoms with the alkaline earth atoms Mg, Ca, and Sr

“…[29][30][31] Details on calculations of atomic spectra of alkaline earth atoms may be found in Refs. [29][30][31][32][33][34][35][36]. Accordingly, only a brief description is presented here.…”

“…The spectra of the valence electrons have been generated by the configuration-interaction plus corepolarization (CICP) method with large mixed Laguerre-type and Slater-type orbital basis sets. 32,33,35 Moreover, the core effects on the valence electrons have been represented by semiempirical polarization potentials in which the cutoff parameters have been obtained by reproducing the experimental energies of the low-lying states of positive ions of the alkaline earth atoms.…”

Generating Phase Shifts from Pseudostate Energy Shifts

“…The treatment of Mg requires the use of a frozen core approximation whose details have been discussed elsewhere [6,24], so only a brief description is given here. The model Hamiltonian is based on a Hartree-Fock (HF) wave function for the Mg ground state.…”

“…One-and twobody core-polarization potentials are then added to the potential. The adjustable parameters of the corepolarization potential are defined by reference to the spectrum of Mg [24].…”

“…The largest calculation was performed with L 14 and L int 3. The parameter L int was set to L int 3 since this is mainly concerned with describing the more quickly converging electron-electron correlations [24]. The secular equations were solved with the Davidson algorithm [11].…”