Calculation of the electronic and photoelectronic spectra of nitroso compounds: a reinvestigation by use of configuration interaction methods

The electronic properties of three selected nitroso compounds: nitrosyl chl oride (NOCl), nitrosomethane (CH3NO) and trichloronitrosomethane (CCl3NO) h ave been compared, and their UV and photoelectron spectra calculated within an extensive configuration interaction treatment. Triple zeta Dunning basis set for NOCl and pseudo potentials basis sets for CX3NO, complemented with Rydberg orbitals for the calculation of the UV sp ectrum have been used. The visible band of the UV spectra of the three comp ounds is attributed to a 1A " state: it is a triplet state for NOCl due to spin-orbit splitting, and a singlet state for the two other compounds. in t he case of NOCl and CH3NO, some Rydberg orbitals are involved in the short wavelengths transitions. However, the corresponding band is poorly resolved in the case of NOCl and not recorded in this region for CH3NO. For CCl3NO, the UV spectrum is much simpler. For the photoelectronic spectra of the three compounds, the presence of a l ow-lying unoccupied orbital located on pi(x(NO))* induces some defect to Ko opmans' theorem and to the one-particle model of ionization. These results imply that the experimental spectrum of NOCl has to be reassigned in this s cheme. (C) 2000 Elsevier Science B.V. All rights reserved.