Positron-atom complexes as quantum halo states

The wave functions of a number of positron-atom complexes are analyzed and three of the systems, namely, e(+)Be, e(+)Na, and e(+)He(S-3(e)), are seen to exhibit quantum halo structures with 45%-50% of their probability distribution lying in the large r classically forbidden region. The mean square distance between the large r fragments (e(+)+Be, Ps+Na+, Ps+He+) for these systems range from 1.8 to 2.2 times larger than the square of the classical turning point, another indication of their halolike nature.