Ab initio calculations for inner-shell ionized and excited states of molecular pyridine clusters

Ab initio calculations are applied to the inner-shell ionizations and excitations of molecular pyridine clusters. We found theoretically that the C 1s -> pi* transition is red shift while the N 1s -> pi* transition is blue shifted. The red shift and blue shift increase with increasing cluster size. The ground state geometries of pyridine dimers and trimers are electrostatically stabilized with the molecular dipole anti-parallel to each other. The physical origin of the blue shifts in the N 1s regime is essentially ascribed to electrostatic interactions.