The low-lying states of the scandium dimer

Abstract

A systematic investigation of low-lying states of Sc(2) using multireference perturbation theory (NEVPT2 and NEVPT3) indicates that the ground state of this system is 5 Sigma(u) with r(e)= 2.611 angstrom, w(e)= 241.8 cm(-1), and De= 1.78 eV. This state is closely followed by other low-lying states of Sc(2): (3)Sigma(u)-, (5)Delta(u), (3)Pi(g), (1)Pi(g), and (1)Sigma(u)-. Our energy ordering of the (5)Sigma(u)- and (3)Sigma(u)- states confirms the recent MRCI results of Kalemos et al. [J. Chem. Phys. 132, 024309 (2010)] and is at variance with the earlier diffusion Monte Carlo predictions of Matxain et al. [J. Chem. Phys. 128, 194315 (2008)]. An excellent agreement between the second-and third-order NEVPT results and between the computed and experimental values of omega(e) (241.8 versus 238.9 cm(-1)) for the (5)Sigma(u)- state suggests high accuracy of our predictions. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3442374]