Photoelectron Spectra of Unsaturated Oxides. I. 1,4-Dioxin and related systems

The He (Iα) photoelectron spectra of the four unsaturated oxides 3,4‐dihydropyran (6), γ‐pyran (7), 2, 3‐dihydro‐1, 4‐dioxin (9) and 1, 4‐dioxin (10) are reported and analysed. Band assignments are based on ab‐initio calculations, using the STO‐3G basis set. The proposed orbital sequences (with reference to the coordinate systems given in Table 1) are, for the top three orbitals: 6, π, nσ, nπ; 7, 3b1(π), 1a2(π), 11a1(σ); 9, 11b(π), 12a(σ), 11a(π); 10, 2b3u(π), 1b1g(π), 6ag(σ). Finally the (almost) localized π‐orbitals have been computed by the Foster‐Boys localization procedure.