PHOTOCHEMICAL-REACTIONS OF SILYLENE WITH ETHENE AND SILENE

To obtain insight into the photochemical behavior of silylene (SiH2), the reactions of silylene in its first two excited states (B-3(1), B-1 (1)) With ethene and silene are studied. The potential energy surfaces (PESs) governing these reactions are calculated by ab initio methods. Our calculations show that minima of the PES describing the reactions of SiH2(B-1(1)) result from an avoided crossing between the two lowes t singlet states. As a consequence, the products of these reactions po ssess quite unusual equilibrium geometries. Furthermore, using estimat es based on the Landau-Zener model, we expect the internal conversion from the excited singlet states to the ground-state PESs to be very ef ficient. Hence the main final products of the reactions starting from the B-1(1) state will be thermally highly excited ground-state molecul es. While the reactions of SiH2(B-1(1)) are found to be strongly influ enced by the electronic ground state, the reactions of the triplet sta tes do not feature crossing with any of the singlet PESs in the vicini ty of the minimum energy path. Furthermore our analysis allows us to r ationalize the trends in the stabilization energies of the various rea ctions.