Ab initio CI calculations of electronic and vibrational spectra of diazomethane Original Research Article

The IR, photoelectron and VUV spectra of the diazomethane molecule were calculated at the MP2 and CI ab initio levels. These calculations enabled the experimentally observed spectra to be assigned. The first broad band of the electronic spectrum of CH2N2 at 3.14 eV results from a forbidden B1 → B2 transition (A2 state). In the UV region up to the first IP (8.90 eV) several Rydberg transitions were calculated (B1 and A1) that could be unambiguously assigned through oscillator strength calculations and analysis of Mulliken populations of diffuse orbital. The first allowed valence band corresponds to a π → π∗ (b1 → b1) transition calculated at 7.65 eV.