Rejection of the C-7(-) diffuse interstellar band hypothesis

Using the new high-resolution (similar to8 km s(-1)) echelle spectrograph o n the 3.5 in telescope at the Apache Point Observatory, we have begun a hig h-sensitivity survey of the diffuse interstellar bands (DIBs) in a large sa mple of reddened stars. Now that we are 2 years into this long-term survey, our sample includes over 20 reddened stars that show at least one of the D IBs that had been suggested to be caused by C-7(-), based on the gas-phase measurement of the C-7(-) spectrum by J. P. Maier's group. The high-quality astronomical data from this larger sample of stars, along with the spectro scopic constants from the new laboratory work recently reported by Maier's group, have enabled us to examine more carefully the agreement between C-7( -) and the DIBs. We find that none of the C-7(-) bands match the DIBs in wa velength or expected profile. One of the DIBs (lambda 5748) attributed to C -7(-) is actually a stellar line. The two strongest DIBs attributed to C-7( -) (lambda 6270 and lambda 4964) are not correlated in strength, so they ca nnot share the same carrier. On the whole, we find no evidence supporting t he hypothesis that C-7(-) is a carrier of the DIBs.