Test study on the excitation spectra of the CO-He van der Waals molecule

In the present contribution we performed ab initio Moller-Plesset perturbat ion theory to fourth order (MP4) and coupled-cluster CCSD(T) calculations i n the framework of the supermolecule approach on the vertical excitation sp ectra of the weakly bound van der Waals GO-He molecule in its "near T-shape d" most stable ground state structure. They indicate that the excited Co(a( 3)Pi)-He(S-1) triplet interaction has R-e = 3.47 Angstrom, D-e = 22.87 cm(- 1) and D-o = 6.07 cm(-1) for CO((3)A ')-He(S-1), and R-e = 3.41 Angstrom, D -e = 24.90 cm(-1) acid D-o = 7.46 cm(-1) for the CO((3)Angstrom ")-He(S-1) electronic state. They also indicate an excited CO(A(1)Pi)-He(S-1) singlet interaction with R-e = 3.49 Angstrom, D-e = 20.92 cm(-1) and D-o = 5.05 cm( -1) for CO(1A ')-He(S-1), and R-e = 3.37 Angstrom, D-e = 27.21 cm(-1) and D -o = 8.24 cm(-1) for the CO(1A ")-He(S-1) state. (C) 2001 Elsevier Science B.V. All rights reserved.