From a structural point of view, the C 18 -(CO) n (n = 6, 4, and 2), like C 18 ring, present a polyynic skeleton with alternating long and short bonds. Based on the geometry and wavefunction generated at the level of B97XD/def2-TZVP, we simulated the scanning tunneling microscope (STM) image of the precursors C 18 -(CO) n (n = 6, 4, and 2) in the gas phase, as displayed in Fig. . It can be seen that the tunneling current is relatively prominent over the short C-C bonds, corresponding to gray or white on the STM image. In contrast, almost no tunneling current is detected on the long C-C bonds, because the local density-of-state (LDOS) of the highest occupied molecular orbitals (HOMOs) show nodal planes in these regions. This character of STM of cyclocarbon oxides is very similar to that of C 18 , exhibiting similarity between their electronic structures . For details and meanings of STM image simulation, please refer to the supplementary material of Ref. .