To address this issue, in Fig. , we decorated the external rim of 2T-N with a variable number of N atoms. The two molecules, 2T-3N and 2T-4N' (structural isomer of the system in Fig. ), have C 2v and C S symmetries, respectively, so that degenerate states are not possible. Comparing with Fig. panel a, as relevant to 2T-N, all spectral features move to the blue upon increasing the number of N atoms in the external rim. Most importantly, the lowest energy transition, strictly forbidden in either 2T-N or 2T-7N, acquires sizable intensity.