Small carbon chains in circumstellar envelopes

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Observations were made for a number of carbon-rich circumstellar envelopes using the Phoenix spectrograph on the Gemini South telescope to determine the abundance of small carbon chain molecules. Vibration-rotation lines of the ν₃ antisymmetric stretch of C₃ near 2040 cm⁻¹ (4.902 μm) have been used to determine the column density for four carbon-rich circumstellar envelopes: CRL 865, CRL 1922, CRL 2023 and IRC +10216. We additionally calculate the column density of C₅ for IRC +10216, and provide an upper limit for 5 more objects. An upper limit estimate for the C₇ column density is also provided for IRC+10216. A comparison of these column densities suggest a revision to current circumstellar chemical models may be needed.