Electron Spin Resonance Spectra of ClCO and ClOO

We have observed the electron spin resonance (ESR) spectra of ClCO and ClOO trapped in polycrystalline CO and Ar, respectively, at 4°K. The radicals were prepared by reaction of a Cl atom, produced by photolytic decomposition of Cl2, with CO and O2. The ESR spectra of these radicals are complicated by, among other things, the Cl nuclear quadrupole interaction. For ClCO the g factor tensor is gz = 1.9980, gx = 2.0061, gy = 2.0003; the hyperfine splitting (hfs) tensor is Az = 227, Ax = 58, Ay = 50 MHz; and the nuclear quadrupole coupling constants are e2Qq = 76 MHz and η = 0.25. For ClOO these spin Hamiltonian parameters are: gz = 2.0100, gx = 1.9987, gy = 1.9915 ; | Az | = 50, | Ax | = 9, | Ay | = 16 MHz; and e2Qq = 105 MHz. The z principal axis is along the Cl bond, and the x principal axis is perpendicular to the molecular plane. The signs of the hfs tensor components of ClCO were assigned in accordance with previous results for FCO. This assignment led to a value of 0.42 for the unpaired electron density in the Cl 3p orbital of ClCO.