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

Abstract

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, 3 nπ * and 1, 3 ππ *. The UV-photoelectron spectrum has been reconsidered by means of MRD–CI, Green's function and the non-diagonal TDA method; the first five IPs are as previously determined. This leads to the ionisation order: 2A 1(11a −1 1)< 2B 2(7b −1 2)< 2B 1(2b −1 1)< 2A 2(1a −1 2)< 2A 1(10a −1 1) . 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.