ELECTRONIC ABSORPTION-SPECTRA OF LINEAR CARBON CHAINS IN NEON MATRICES .2. C-2N(-), C-2N, AND C2NH

Absorption spectra observed between 400 and 2500 nm in 5 K neon matrices have been assigned to electronic transitions of linear C2n - (n=2-10): 2Π←X2Π, C2n (n=3-7): 3Σu-←X3Σ g-, and C2nH (n =3-8): 2Π← X2Π chains. The species have been produced by mass selected deposition of cations or anions produced in a hot cathode discharge source (C2n, C2n, C2nH) and by laser vaporization of graphite (C2n, C2n). In addition to experimental and chemical evidence, the dependence of the absorption wavelength on the number of carbon atoms was used to assign the electronic transitions. Infrared absorptions which were recorded around 2000 cm-1 are attributed to asymmetric stretching frequencies of C8, C10, and C12. This is based on correlation of their intensities with the identified electronic bands. The possible relevance of the electronic spectra of these carbon chains to astrophysical observations of diffuse interstellar bands is discussed. © 1995 American Institute of Physics.