THE ELECTRONIC STATES OF THE AZINES .5. PYRIDAZINE, STUDIED BY VUV ABSORPTION, NEAR THRESHOLD ELECTRON ENERGY-LOSS SPECTROSCOPY AND ABINITIO MULTIREFERENCE CONFIGURATION-INTERACTION CALCULATIONS

A comparison of VUV absorption with near-threshold electron energy-loss spectra, has led to the identification of several new low-lying electronic states of pyridazine. The assignment of these and previously known singlet states is discussed in the light of large-scale all-valence electron CI calculations using a multi-reference, multi-root CI (MRDCI) study, which includes Rydberg orbitals in the basis set. The UV-photoelectron spectrum is reconsidered in the light of these calculations and it is concluded that IP2 is of 2B1 rather than 2A2 symmetry. The ground state molecular electronic properties are evaluated with a large SCF/CI basis, and compared with available experimental data.