A joint experimental and theoretical approach has been used to study the valence shell electronic
structure and photoionisation dynamics of s-triazine (1,3,5-triazine). Synchrotron radiation has been
employed to record angle resolved photoelectron spectra of the complete valence shell for photon energies
between 17.5 and 100 eV, thereby allowing photoelectron anisotropy parameters and branching ratios to
be determined. Absolute photoionisation partial cross sections have been estimated as the product of
these branching ratios and the absolute photoabsorption cross section. The Kohn–Sham and the timedependent
version of density functional theory methods have been used to calculate photoelectron
anisotropy parameters and photoionisation partial cross sections, and these have been compared with
the corresponding experimental data. The calculations predict that shape resonances affect the photoionisation
dynamics of several of the molecular orbitals. The angle resolved photoelectron spectra suggest
that the 1a00
2(p) orbital is more tightly bound than the 5e0(r) orbital, and that the 4a0
1(r) orbital is
more tightly bound than the 1a0
2(r) orbital, in agreement with the predicted molecular orbital sequence.
For the outer valence orbitals the single-particle picture of ionisation holds but electron correlation becomes
increasingly important for the inner valence 4e0, 3e0 and 3a0
1 orbitals and leads to a redistribution of intensity.
Instead of a readily distinguishable main-line, associated with each of these orbitals, the photoelectron
intensity is spread over numerous satellite states and the resulting band is broad and featureless.
