Long-lived diatomic dications: potential curves and radiative lifetimes for CaBr2+ and CaI2+ including relativistic effects

Abstract

Relativistic effective core potential calculations have been employed in the framework of a spin–orbit configuration interaction to compute the lowest-lying electronic states of the CaBr2+ and CaI2+ dications, and the results are compared with the data for the isovalent CaCl2+ system studied earlier. The ground X2Π state in all three dications arises from a strong polarization of X(2P°)(X= Cl, Br or I) by the Ca2+(1S) ion and is bound by 0·96–1·55eV with respect to the corresponding diabatic dissociation limits. It is split by the spinorbit interaction into the X1 2Π3/2 and X2 2Π1/2 components, with the energy splittings calculated to be 647 cm-1(CaCl2+), 2115 cm-1(CaBr2+) and 3544 cm-1(CaI2+). The X1 and X2 states are found to be thermodynamically stable in CaCl2+ and CaBr2+, while in CaI2+ the lowest dissociation limit, Ca++(2S)+ I+ 3P2), lies 1700 and 5200 cm-1 lower than the X1 and X2 minima respectively. The X1 and X2 states in CaI2+ are extremely long-lived, however, owing to the high and very broad...