PHOTOELECTRON-SPECTRA OF THE ISOMERS OF METHOXYPYRIDINE

The He I photoelectron spectra of 2-, 3- and 4-methoxypyridine are rep orted 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 exper iment and shows quantitatively the importance of incorporating both co rrelation and relaxation effects. Comparison of experimental and ab in itio ionization energies of the methoxypyridines with the semi-empiric al HAM/3 method further substantiates the utility of HAM/3 for the int erpretation of photoelectron spectra.