Finally, for set B, we also show the average Fe-N bond lenghts of the geometries where S 1 /S * 0 transitions occur (orange lines) in Figure (b). The average Fe-N distances differ to a similar extent as the values at the intersystem crossing geometries from their Franck-Concon references. The large variation in the geometries in this set is also displayed as a superposition of structures in Figure . This highlights the large extent of the region on the potenital energy surface, where polyatomic molecules can undergo transitions between electronic states.