A THEORETICAL-STUDY OF THE GEOMETRY AND ELECTRONIC-SPECTRA OF DIOXIRANE, DIOXYMETHANE AND ITS ANION

Dioxirane, dioxymethane, and the dioxymethane anion have been studied using multiconfigurational SCF and second-order perturbation theory (CASSCF/CASPT2). The equilibrium geometries of the three systems have been determined for the lowest electronic states. The lowest excited state in dioxirane was found at 4.1 eV, in agreement with experimental evidence. The electron affinity is computed to be 2.0 eV. The ground state of dioxymethane is located 0.5 eV above dioxirane. The isomerization barrier from dioxirane is 1.1 eV. Dioxymethane has seven excited states below 2 eV. The lowest triplet state is located only 0.5 eV above the ground state. The dioxymethane anion is a 3 pi-electron system with a geometry similar to dioxymethane. The first 4 pi-electron state is located 0.3 eV above and has a structure intermediate between dioxirane and dioxymethane. Two more excited states of the anion have been located below 2 eV.