2 research outputs found
Two-electron atoms, ions and molecules
The quantum mechanics of two-electron systems is reviewed, starting with the
ground state of the helium atom and helium-like ions, with central charge . For Z=1, demonstrating the stability of the negative hydrogen ion, H,
cannot be achieved using a mere product of individual electron wave functions,
and requires instead an explicit account for the anticorrelation among the two
electrons. The wave function proposed by Chandrasekhar is revisited, where the
permutation symmetry is first broken and then restored by a counter-term. More
delicate problems can be studied using the same strategy: the stability of
hydrogen-like ions for any value of the proton-to-electron mass
ratio ; the energy of the lowest spin-triplet state of helium and
helium-like ions; the stability of the doubly-excited hydrogen ion with
unnatural parity. The positronium molecule , which has been
predicted years ago and discovered recently, can also be shown to be stable
against spontaneous dissociation, though the calculation is a little more
involved. Emphasis is put on symmetry breaking which can either spoil or
improve the stability of systems.Comment: 16 pages, 2 figure