Journal Article Research Support, Non-U.S. Gov't electron density analysis excited states interacting quantum atoms Furans Heterocyclic Compounds Hydrocarbons, Aromatic Protons Pyrroles Thiophenes UC0XV6A8N9 aromatic molecules atomic energies chromophore conical intersections conjugated molecules electron delocalization energy transfer furan hydrogen-hydrogen bonding interacting quantum atoms (IQA) nonaromatic molecules quantum theory of atoms in molecules (QTAIM)