Loop currents in chlorophyll a

Loop currents involve the circulation of electrons (or holes) around closed conjugated-bond loops. From the length of the orbital perimeter the kinetic energy per electron can be calculated. In chlorophyll a, four electronic excitations have been analyzed, including: (1) a single positive charge (hole) circling a 19-bond orbit with a Möbius twist (this is proposed as the effective ground state); (2) nine electrons, unevenly spaced, circling the same 19-bond orbit but without the Möbius twist (proposed as the red excited state); (3) nine electrons in the same orbit but evenly spaced and vibrationless (the hopping exciton); (4) ten electrons, unevenly spaced, in a 16-bond orbit (the blue excited state). The fit of theory to experiment is examined.