Ž . Chemical Physics 228 1998 293–299 Electronic spectra of linear carbon anions Marek Tulej, David A. Kirkwood, Gianni Maccaferri, Otto Dopfer ) , John P. Maier Institute for Physical Chemistry, UniÕersity of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland Received 15 September 1997 Abstract Resonance enhanced two colour photodetachment spectroscopy has been employed to probe several electronic transitions of mass selected anionic carbon chains in the gas phase. Spectra of the A 2 P § X 2 P transition of C y ,A 2 P § X 2 P g u 5 u g and B 2 P § X 2 P transitions of C y and A 2 P §X 2 P ,B 2 P § X 2 P and C 2 P § X 2 P transitions of C y u g 7 g u g u g u 9 Ž . 2 were obtained, yielding origin bands significantly narrower than those reported previously. In addition, two x P § u 2 Ž . y y1 X P x s 2,3 electronic transitions of C with band origins at 25989 and 28717 cm have been detected. The g 4 improvements in the resolution and extended scan range of the spectra have enabled values for the gas to neon matrix shift for the vibronic bands to be inferred. Comparison of the observed transitions with the tabulated diffuse interstellar bands y Ž . indicate that none of these are due to C n - 10 . q 1998 Elsevier Science B.V. n 1. Introduction The gas phase study of clusters and molecules of carbon, the third most abundant element in the uni- verse, is an area of scientific research which has witnessed continued expansion over the last few decades. In particular the discovery of fullerenes and their subsequent synthesis in macroscopic quantities has played a crucial role in stimulating such interest wx 1 . The astronomical identification of small carbon radicals and molecules in interstellar molecular wx clouds and certain stellar bodies 2 has led to specu- lation that the series of, as yet, unidentified absorp- Ž . tions known as the diffuse interstellar bands DIBs wx may also be due to either pure 3 or functionalised w x poly-carbon species 4,5 . A myriad of studies have been carried out on carbon clusters in general, although to date there is a ) Corresponding author. relative paucity of information concerning their elec- tronic states. Carbon cluster cations have largely been probed from a mass spectrometric approach with a view to obtaining information on the geomet- wx rical structure of these species 6 . Experiments on neutral carbon molecules include infrared spec- Ž . wx troscopy of C n F 13 7 and electronic studies of n Ž . wx CH in neon matrices n F 15, m s 0,1 8. n m Investigations of carbon anions have traditionally y wx concentrated on C 9 , the first anion for which a 2 rotationally resolved electronic spectrum was ob- w x tained 10 . Much of the existing knowledge on the y Ž . y Ž electronic spectra of C n s 2–10 and C n 2 n 2 nq1 . s 2–6 comes from matrix studies, which have wx been the subject of a recent review 8 . These incor- porate direct absorption spectroscopy of mass se- lected carbon chains embedded in 5 K neon matrices. Subsequent experiments used the matrix data on the even numbered chains C y ,C y and C y to examine 4 6 8 their C 2 P § X 2 P electronic transitions in the gas 0301-0104r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. Ž . PII S0301-0104 97 00358-3