The electronic states and molecular properties of 1,2,3-triazine studied by VUV absorption, near-threshold electron energy-loss spectroscopy and ab initio multi-reference configuration interaction studies Original Research Article

Optical electronic absorption spectra, and electron energy-loss spectra have been obtained for 1,2,3-triazine. The valence and Rydberg excited states have been studied by multi-reference multi-root configuration interaction studies using MRD–CI techniques, and the results related to the experimental spectra. A number of Rydberg states, associated with five ionisation limits, have been identified along with valence states of types 1, 3nπ* and 1, 3ππ*. The UV-photoelectron spectrum has been reconsidered by means of MRD–CI, Greenʹs function and the non-diagonal TDA method; the first five IPs are as previously determined. This leads to the ionisation order:2A1(11a−11)<2B2(7b−12)<2B1(2b−11)<2A2(1a−12)<2A1(10a−11) .The electronic properties of the molecule have been determined at the equilibrium geometry for a large basis set at both the SCF and MP2 levels.