The U.V. spectra of dibenz-1,4-dioxin and 1,4-benzdioxin and the E.S.R. spectra of their monopositive ions

P-method calculations have been carried out on two non-planar dioxins to study the applicability of the method to such systems. The E.S.R. spectra have also been calculated using standard techniques for open-shell systems to test further the π-electron separability theorems.