The spectroscopic and molecular constants studies of the ground and first excited states of O2 molecule by CCSD(T) and MRCI methods

Abstract

The potential energy curves of the ground and first exicted states were calculated by CCSD(T) and MRCI methods. Effects of the core-valence correlation and relativistic corrections on the the potential energy curves are included in present calculation. To obtain reliable results, the Davidson modification (MRCI+Q) which is compensate for the high order truncation is also considered in present calculation. Furthermore, in order to avoid the basis set superposition error, the complete basis set limit extrapolation is also included in present calculation. With these potential energy curves, the spectroscopic parameters are determined and compared with available theoretical and experimental studies. The result indicated that present results are in good agreement with experimental data and the core-valence correlation correction has larger effects on the spectroscopic constants than relativistic correction.