The obtained TD-DFT results are employed to simulate the absorption spectra of these polyynes, as shown in Fig. (a). It can be seen that the 1 1 Σ u + ← X 1 Σ g + absorption bands of the carbon chains H-(C≡C) n -H (n = 3-9) are all derived from the transition from the ground state S 0 to a relatively high excited state S n (n = 7, 8, or 10).