The spectrum of comet Cunningham, 1940C.

Slit spectrograms of Comet Cunningham secured at the McDonald Observatory reveal well-resolved ultraviolet bands due to OH and NH; only the lines of low rotational quantum number are observed, as in the case of CH. The abundances of OH and NH molecules seem to be of the same order as that of CN. Each branch of the violet bands of CN has two maxima, one corresponding to a rotational distribution for T 400° K and one corresponding to T 50° K. The tail bands of CN are absent. The authors discuss the variation with heliocentric distance of the relative intensities of the vibrational transitions. The rotational intensity distribution and the extension of the different bands in the head have been investigated. The cometary bands of CH belonging to the two electronic transitions, A2∆ → x2∏ (near λ 43oo) and B2∑- → x2∏ (near λ 3900), are described. The bands observed between λ 4000 and λ 4130 are discussed but remain unidentified