Investigating the Temperature Distribution of Diatomic Carbon in Comets Using the Swan Bands

We present high spectral resolution observations of comets 122P/de Vico and 153P/Ikeya–Zhang obtained with the Tull Coudé spectrograph on the 2.7 m Harlan J. Smith telescope of McDonald Observatory. We used these data to study the distribution of the lines of the C2 (Swan) bands. We show that the data are best represented with two rotational temperatures, with the lowest energy lines being at a relatively cool temperature and the higher energy lines being at a higher temperature. We discuss the implications of this two-temperature distribution and suggest future work.