Excitation temperature of C2 and broadening of the 6196 Å diffuse interstellar band

This paper presents a finding of the correlation between the width of a strong diffuse interstellar band at 6196 A and the excitation temperature of C 2 based on high resolution and high signal-to-noise ratio spectra. The excitation temperature was determined from absorption lines of the Phillips $\rm A^{1}\Pi_u-X^{1}\Sigma^{+}_g$ and Mulliken $\rm D^{1}\Sigma^{+}_u-X^{1}\Sigma^{+}_g$ systems. The width and shape of the narrow 6196 A DIB profile apparently depend on the C 2 temperature, being broader for higher values.