The electronic absorption spectra of HC2n+1H and HC2n+1H+ (n=2-7) in neon matrices have been obtained. The species were prepared by codeposition of mass selected HC2n+1H+ ions with neon at 5 K. For each species the O-0(0) band of the electronic transition as well as frequencies or fundamental vibrations in the excited state have been determined. The wavelength of the origin band in this homologous series is linearly dependent on the number of carbon atoms. Isotopic labeling supports the vibrational assignment and confirms the presence of two equivalent hydrogen atoms for HC2n+1H and HC2n+1H+ Based on spectroscopic considerations, a linear geometry is assumed with one hydrogen atom located at each end, and that the observed spectra of HC2n+1H are their 3 Sigma(u)(-) <-- X (3) Sigma(g)(-) transition.