STUDY OF THE LOW-LYING STATES OF NIO- AND NIO USING ANION PHOTOELECTRON-SPECTROSCOPY

The 2.33 and 3.49 eV photoelectron spectra of NiO- obtained with a new apparatus using field-free electron energy analysis are reported. The electron affinity of NiO is determined to be 1.470(3) eV. A spin-orbi t splitting of 260(40) cm(-1) for the ground (2) Pi anion state is obs erved. A bond length of 1.668(4) Angstrom and vibrational frequency of 660(40) cm(-1) are determined from spectral simulations of the neutra l (3) Sigma(-) ground state <-- anion (2) Pi(3/2) State transition. A transition from an excited (4) Sigma(-) anion state [T-e = 900(40) cm( -1), omega = 760(40) cm(-1)] to the ground neutral state is assigned. New spectroscopic constants are obtained for the (3) Phi state [T-e = 0.65(1) eV], the (1) Delta state [T-e = 0.94(1) eV, omega = 615(15) cm (-1) and r(e) = 1.600(6) Angstrom] and the second (3) Pi state [T-e = 1.194(10) eV, 2A = 411(30) cm(-1)]. These findings are in general agre ement with these recently reported by Wu and Wang [J. Chem. Phys. 107, 16 (1997)], although several reassignments of the photoelectron spect ra (PES) are made based on comparison with calculations and newly reso lved fine structure. (C) 1998 American Institute of Physics.