Optical properties of six isomers of three dimensionally delocalized π-conjugated carbon nanocage Yoshifumi Noguchi, Daichi Hirose and Osamu Sugino Eur. Phys. J. B, 91 6 (2018) 125 Published online: 18 June 2018 DOI: 10.1140/epjb/e2018-90112-y