Ab initio MRD-CI investigation of the electronic spectrum of glyoxal (CHO)(2)

摘要

Multireference configuration interaction (MRD-CI) calculations are used to compute the electronic spectrum of glyoxal (CHO)(2), a key species in atmospheric chemistry. The calculations place the first dipole-allowed transition 1(1)A(u)<- X(1)A(g) at 2.80 eV (442.8 nm) with an oscillator strength of 0.0002 and the dipole forbidden 1(1)B(g)<- X(1)A(g) transition at 4.22 eV (293.8 nm), in accordance with prior experiments. In addition, a much stronger transition (3(1)B(u)<- X(1)A(g)) at 8.51 eV (145.7 nm) is predicted, which has not yet been reported in the literature. This transition corresponds to 1bg -> 2a(u) excitation and can be characterized as pi(CO)->pi*(CO) type in accordance with the computed relatively large oscillator strength f = 0.38. The corresponding triplet states are also computed.