On the possibility of binding of two electrons to dipole potentials

The possibility of binding two electrons by the fixed finite dipole (FFD) p otential due to two point charges + qe and - qe separated by the distance R is explored at the full configuration interaction level with extended basi s sets. The critical value of the dipole moment mu = qR required to bind tw o electrons tends to infinity for small q (q approximate to 0.91e) and decr eases precipitously as q increases. In the limit of very large q land small R), this critical dipole moment seems to approach a limit below 2 Debyes ( D). It is shown analytically that in the point dipole limit this critical d ipole value will approach that for binding a single electron. An extension of the FFD model to include effects of inner-shell core electrons allows th e Li-, Na-, and K- cases (with a -1e charge at R) also to be examined. FFD- plus-core systems display even larger critical dipoles (113, 129, and 141 D , respectively) than does the + qe / - qe FFD potential (92.2 D). These fin dings suggest that it will be difficult to find a real molecule that can bi nd (by approximate to 1 cm(-1)) two electrons via its dipole potential. Fin ally, a simple electrostatic model is introduced which permits the critical dipole value of the FDD and its core-orbital extension to be evaluated rat her well. (C) 2000 John Wiley & Sons, Inc.