THEORETICAL AND EXPERIMENTAL STUDIES OF THE VALENCE PHOTOEMISSION SPECTRUM OF PROPIONITRILE

The valence photoemission spectrum of propionitrile for all outer and inner valence levels up to the ionization energy of 23 eV is calculate d by ab initio third-order algebraic diagrammatic construction (ADC(3) ) Green's function method. The spectrum is also measured by high resol ution He I photoelectron spectroscopy to resolve additional spectral f eatures mainly due to the vibronic excitations. The present (ADC(3)) c alculation provides a fairly good description of the vertical-electron ic ionization spectral features of the valence PES spectrum of propion itrile. From the ionization threshold up to and including the 8a' ioni zation, the ionization phenomena appear essentially as one-particle pr ocesses. For 11a' and 10a' ionization, the hole mixing occurs between this pair of ionization of the same symmetry, although the hole mixing is not so significant as ill molecules containing several CN groups. For the innermost 7a' band, the breakdown of the one-electron picture occurs.