THE ELECTRONIC STATES AND MOLECULAR-PROPERTIES OF 1,2,3-TRIAZINE STUDIED BY VUV ABSORPTION, NEAR-THRESHOLD ELECTRON-ENERGY-LOSS SPECTROSCOPY AND AB-INITIO MULTIREFERENCE CONFIGURATION-INTERACTION STUDIES

Optical electronic absorption spectra. and electron energy-loss spectr a have been obtained for 1,2,3-triazine. The valence and Rydberg excit ed states have been studied by multi-reference multi-root configuratio n interaction studies using MRD-CI techniques, and the results related to the experimental spectra. A number of Rydberg states, associated w ith five ionisation limits, have been identified along with valence st ates of types (1,3)n pi and (1,3)pi pi*. The UV-photoelectron spectru m has been reconsidered by means of MRD-CI, Green's function and the n on-diagonal TDA method; the first five IPs an as previously determined . This leads to the ionisation order: (2)A(1)(11a(1)(-1)) < B-2(2)(7b( 1)(-1)) < B-2(1)(2b(1)(-1)) < (1)A(2)(1a(2)(-1)) < (2)A(2)(10a(1)(-1)) . The electronic properties of the molecule have been determined at th e equilibrium geometry for a large basis set at both the SCF and MP2 l evels. (C) 1998 Elsevier Science B.V.