Polyynes and Interstellar Carbon Nanoparticles

Laboratory experiments show that long-chain polyyne molecules are often components of the type of carbon nanoparticle (CNP) that can be associated with the infrared (IR) emission bands attributed to polycyclic aromatic hydrocarbons (PAHs). These molecules are attached to peripheral sites on PAH molecules and have in excess of six carbon atoms. IR spectra of CNPs containing a variety of sp-bonded carbon chains in conjunction with PAH groups are reported in this paper. We find that polyyne side-chains produce several notable spectral features in the 4.3 and 5.7 μm (2300–1750 cm −1 ) range, some of which may be present in interstellar emission. A deeper search for these features in absorption or emission in interstellar sources would indicate if polyyne chains are commonly attached to PAH emitters.