Photoelectron spectrum and structure of B2O2

The He i photoelectron spectrum of B2O2 is presented. A comparison of ab initio molecular orbital calculations and the observed spectrum provides the most conclusive evidence to date that the geometrical structure is D∞h O–B–B–O. Even though the experiment is conducted at 1200 °C, vibrational structure is evident in the first two bands. A complex Franck–Condon fitting is used to infer the geometrical changes occurring when the various ionic states are formed. The results are in fairly good agreement with ΔSCF calculations. The orbital ordering in B2O2, πg,πu,σg,σu differs from that in the isoelectronic molecule C2N2.