ELECTRONIC SPECTROSCOPY OF CARBON CHAINS AND RELEVANCE TO ASTROPHYSICS

Laboratory measurements of electronic transitions in carbon chains are presented. Guided by the results found in neon matrices, gas-phase sp ectra have been obtained with two different experimental approaches. E lectronic transitions of neutral carbon chains are detected in a super sonic slit jet plasma by cavity ring-down (CRD) spectroscopy, and thos e of mass-selected anions are probed by resonant two-colour electron p hotodetachment. The successful combination of matrix and gas-phase exp eriments is demonstrated for the examples of C6H and C14H-. These, and other previous measurements on electronic transitions of long carbon chains in the gas phase, are compared with the tabulated wavelengths o f the diffuse interstellar bands. In the case of the A (2)Pi(u)-X (2)P i(g) transition of C-7(-) the origin and three intense bands in the ga s-phase spectrum match, within +/- 0.2 nm error limits, diffuse inters tellar bands which have comparable FWHMs and equivalent widths.