Electronic Structures and Spectra of Triatomic Oxide Molecules

Existing knowledge of the forms and the electronic spectra of a series of triatomic oxide and similar molecules BAB are briefly reviewed. The evidence (mostly from infra-red data) which establishes the acute-angled model of ozone as very probably correct is reviewed, one or two new points being added. New conclusions concerning the probable electronic structure of ozone are given. A new diagram is introduced showing the ionization energies of the various normal and excited valence-shell molecular orbitals as a function of the apex angle BAB. It is shown that this diagram, or a similar diagram, may be very useful in understanding the electronic structures and spectra of the molecules considered. The diagram makes possible a number of predictions which may be tested experimentally. The forms of the molecular orbitals of C${\mathrm{O}}_2$ are reviewed, with some interesting new modifications.