Moreover, they are also detected as intermediates in the formation of polyaromatic hydrocarbons and fullerenes . The recent successful synthesis and characterization of cyclo carbon by condensed phase experiments evokes another long-hidden identity to carbon chains, that is, they may be the ring-opening products of such chemically unstable carboatomic rings . While conducting theoretical researches on cyclo carbon and its analogues and derivatives , we are also interested in the properties of these carbon chains of different lengths. Since the electronic spectra of cyclic carbon clusters have already been extensively explored , the related properties of chain-shaped species H-(C≡C) n -H with similar electronic structure become a subject worthy of study.