Electronic structure of chromium oxides, CrOn- and CrOn (n=1-5) from photoelectron spectroscopy and density functional theory calculations

The electronic structure of CrOn- and CrOn (n=1-5) was investigated using a nion photoelectron spectroscopy and density functional theory. Photoelectro n spectra of CrOn- were obtained at several photon energies and yielded ele ctron affinities, vibrational and electronic structure information about th e neutral CrOn species. Density functional theory calculations were carried out for both the neutrals and anions and were used to interpret the experi mental spectra. Several low-lying electronic states of CrO were observed an d assigned from photodetachment of the CrO- ground state ((6)Sigma (+)) and an excited state ((4)Pi), which is only 0.1 eV higher. The main spectral f eatures of CrO2- were interpreted based on a C-2v CrO2- (B-4(1)). A very we ak Cr(O-2)(-) isomer was also observed with lower electron binding energies . Relatively simple and vibrationally resolved spectra were observed for Cr O3-, which was determined to be D-3h. The CrO3 neutral was calculated to be C-3v with the Cr atom slightly out of the plane of the three O atoms. The spectrum of CrO4- revealed a very high electron binding energy. Several iso mers of CrO4- were predicted and the ground state has a distorted tetrahedr al structure (C-2) without any O-O bonding. Only one stable structure was p redicted for CrO5- with a superoxo O-2 bonded to a C-3v CrO3. (C) 2001 Amer ican Institute of Physics.