CN rotational excitation

The results of a search for new lines of sight in which to study the CN excitation and a statistical analysis of all the excitation temperatures measured using interstellar CN, are reported. This data set strongly confirms that the cosmic background radiation (CBR) is the dominant contributor to the excitation of CN, and demonstrates the homogeneity of the CBR. Thirty-five observations is a sufficiently large sample to look for the presence of systematic effects in the CN excitation