Diatomics AB (AÂ =Â Be, Mg; BÂ =Â O, S) and oligomers thereof: A theoretical study

A quantum chemical study of title systems and some related species (CaO, SrO, BaO and BaPo) was performed by B3LYP, H.F., MP2, TD DFT, and SAC-CI procedures. Structural features of isomers, vibrational frequencies, population analysis, ionization potential and in particular, electronic spectra. Electronic spectra of several monomers exhibit in accordance with experiments, the first electronic transitions in the near IR region (SAC-CI and TD DFT techniques). The passage to oligomers is accompanied by a very significant hypsochromic shift of the longest wavelength bands, increase of ionization potential and decrease of electron affinity.