Theoretical study of the electronic structure of the Ba2 molecule Original Research Article

The electronic structure of Ba2 has been investigated using a 10-electron relativistic pseudopotential, Configuration Interaction with four active electrons and core-polarisation potential. Fine structure has been taken into account through a semiempirical spin-orbit operator. Potential energy curves have been determined for all the molecular states dissociating into Ba(6s2) + Ba(6s2; 6s5d; 6s6p) and spectroscopic constants have been obtained for bound states. Evidence for a doubly excited nature of various excited states is pointed out. The ground state of Ba2 is found to be weakly bound (De = 0.202 eV) at long range (Re = 9.22 a0) with an harmonic frequency ωe = 35 cm−1. The calculated energy for the transition (2)1 Πg-X1εg+ is found to be in very good agreement with an infrared band observed at 850 nm in the absorpt spectrum of Ba2 isolated in solid matrix. Almost all present results are new for excited states.