Shape and Core-Excited Resonances in Thiophene.

We present a comprehensive study of resonance formation in electron collisions with thiophene. Detailed calculations have been performed using the ab initio R-matrix method. Absolute differential cross sections for electron impact excitation up to 18 eV and for two scattering angles, 90 and 135°, have been measured. Agreement between the calculated and measured experimental cross sections is very good. Three shape resonances previously described, two of π* character and one σ*, as well as a number of resonances of core-excited or mixed character are identified and characterized in the calculations. The measured cross sections provide experimental confirmation for a number of the core-excited resonances. The link between these resonances and prior DEA experiments is discussed.