Theoretical study of low-lying electronic states of CuO and CuO-

DFT(B3LYP) calculations on the spectroscopic properties of the low-lying st ates of CuO and CuO- have been carried out. The corresponding electronic sp ectrum has been estimated by using MRSDCI, MP4(SDQ) and CCSD(T) methods. Th e results support the assignment, based on the recent photoelectron spectro scopic (PES) experiment that the state at 1.91 eV is a CuO((4)Sigma(-)) and the CuO((2)Delta) arising from the electron detachment of a 3d electron of CuO- is more than 2.2 eV above the ground state of CuO(X (2)Pi). Our calcu lations suggest that the feature a' in the PES experiment of CuO- should be due to the 1 (1)Pi excited state, rather than due to the spin-orbit splitt ing component of the 1 (3)Pi state as suggested in the PES experiment. (C) 2000 Published by Elsevier Science B.V.