The lowest-lying electronic states of BeMg

In this study, potential energy curves for the lowest-lying electronic states correlating with the first four dissociation channels were determined using the cc-pVQZ basis sets and CASSCF/MRCI wavefunctions. All valence orbitals plus one set of s and p correlation functions were included in the active space. A whole set of spectroscopic constants completes the characterization of each state. In its ground state (X1Σ+), BeMg is weakly bound (De=0.05 eV) and, consequently, has a long internuclear equilibrium distance (Re=3.300 Å, ωe=44.2 cm−1). In previous theoretical works, the internuclear equilibrium distance was calculated to be around 4.5 Å (SCF, CCD, and CEPA methods) and 5.1 Å (QCID method).