Stable negative ions of the heavy alkaline-earth atoms

Abstract

Strontium, barium and radium are predicted to have stable negative ions of ns2np designation, on the basis of eigenchannel R-matrix calculations performed in LS coupling for the negative ion of each alkaline-earth atom. The calculations also confirm earlier studies indicating that the negative ion of calcium is stable and that corresponding 2P degrees states in beryllium and magnesium are unstable shape resonances. The much larger polarisability of the heavier alkaline earths play a crucial role in binding the additional electron. The analysis uses quantum defect theory in its generalised form appropriate for long-range motion in a dipole polarisation potential.

Resonance enhancement of relativistic effects for the scattering of very slow electrons by heavy atoms

“…We found that the 7P»2 level in the Ra negative ion lies in the discrete spectrum (E = -0.0109 Ry; calculations in Ref. [5] give E= -0.0055 Ry) and the 7P3&2 level lies practically on the border between the discrete and continuous spectra (E = 0.0013 Ry with accuracy -0.001 Ry). In our present work we have found that for electron-radium scattering, electron polarization can exceed 90% in the energy interval 0.01 Ry 5 E~0.02 Ry near the scattering angle 0=90'-100'.…”

Electron Affinity of Strontium

“…Theoretical Vosko et al (1989) [12] Froese Fischer (1989) [13] Kim and Greene (1989) [14] Johnson et al (1989) Fuentealba et al (1990) [10] Gribakin et al (1990) [16] Dzuba et al (1991) [17] Cowan and Wilson (1991) [18] Experimental [20] Wilson (1989) …”

Many-Body Calculations of the Electron Affinity for Ca and Sr

“…Several theoretical results were published between 1987 and 1992, most of them in the range from 45 to 82 meV; see Refs. [1,[3][4][5][6][7][8][9].…”