Gas-Phase Electronic Transitions of Carbon Chain Anions Coinciding with Diffuse Interstellar Bands

Abstract

Gas-phase electronic spectra of several carbon chain anions have been measured in the laboratory and compared with diffuse interstellar bands (DIBs). The lowest energy transition of C 7 - shows seven prominent narrow bands, five of which show striking matches with narrow DIBs while the other peaks are obscured by broader, more intense, DIBs. The origin bands in the corresponding spectra of C 6 - , C 8 - , and C 9 - also appear to match DIBs. These observations provide the first compelling evidence for the identification of some DIB carriers. The presented laboratory data on these and other transitions-predicted relative intensities and the rotational profile of the C 7 - origin band at 627.0 nm - provide a unique opportunity for specific astronomical measurements. © 1998. The American Astronomical Society. All rights reserved.