Potential curves for several electronic states of the MgHe, Mg+He, and Mg+2He van der Waals complexes

We have estimated the potential curves of the Mg(3s3p pi). He[(3)Pi], Mg(3p pi 3p pi). He[(3)Sigma(-)], Mg+(3s). He[(2)Sigma(+)], Mg+(3p pi). He[(2)Pi ], and Mg+2(2p(6)). He[(1)Sigma(+)] van der Waals states by means of ab ini tio calculations. Similar to the analogous doubly excited states of MgNe, M gAr, and MgKr, the Mg(3p pi 3p pi). He[(3)Sigma(-)] state is found to be un usually strongly bound, D-e=2386 cm(-1), a bond strength which is an astoun ding 165 times that of the singly excited Mg(3s3p pi). He[(3)Pi] state and 35 times that of the Mg+(3s). He ion. The strong bonding is attributed prim arily to the lack of a Mg(3s) electron, so that all the attractive forces c an extend to smaller internuclear distances because there is no Mg(3s sigma )/He(1s sigma) repulsion. In fact, the Mg(3p pi 3p pi). He[(3)Sigma(-)], Mg +(3p pi). He[(2)Pi], and Mg+2(2p(6)). He[(1)Sigma(+)] states have quite sim ilar bond energies and bond lengths, indicating that for RG=He, the primary attractive force in all these states is the ion/induced-dipole interaction of the "Mg+2/He" core. This is consistent with the fact that the bond ener gy of the Mg(3p pi 3p pi). He[(3)Sigma(-)] state is more than four times gr eater than that of the Mg(3p pi 3p pi). Ne[(3)Sigma(-)] state, where there is substantial Mg(3p pi)/Ne(2p pi) repulsion not present in the Mg(3p pi 3p pi). He[(3)Sigma(-)] state. (C) 1999 American Institute of Physics. [S0021 -9606(99)30635-8].