PHOTOELECTRON-SPECTRA OF THE ISOMERS OF METHOXYPYRIDINE

The He I photoelectron spectra of 2-, 3- and 4-methoxypyridine are reported and interpreted in terms of a composite-molecule model and ASCF/MP ionization energies. For pyridine, this ab initio method correctly locates the nitrogen lone-pair molecular orbital with respect to experiment and shows quantitatively the importance of incorporating both correlation and relaxation effects. Comparison of experimental and ab initio ionization energies of the methoxypyridines with the semi-empirical HAM/3 method further substantiates the utility of HAM/3 for the interpretation of photoelectron spectra.