New optical emission spectra of linear carbon molecules, polyynes C2nH2 (n = 5-8), were observed upon UV-laser excitation of the 0-0 band of the dipole-allowed transition, (1)Sigma(+)(u) <- X-1 Sigma(+)(g), of size-separated polyyne molecules in hexane. The emission spectra of C10H2 showed distinct peaks at 436 and 480 nm with a separation of similar to 2100 cm(-1) for a stretching vibration of the sp-carbon chain. Weak absorption features were also recorded in near-UV regions in shorter wavelengths to compare with the emission spectra. The spectral features in the emission were assigned to the vibronic bands of the forbidden electronic transition, (1)Delta u -> X-1 Sigma(+)(g). (C) 2007 Elsevier B.V. All rights reserved.