The kinetic temperature in the interior of the Xi Ophiuchi cloud from Copernicus observations of interstellar C2

Satellite observations of transitions of C2 at 2312 Angstroms in the spectrum of Xi Ophiuchi were carried out to evaluate the kinetic temperature of the interior cloud. A column density of 1.22 x 10 to the 12th per sq cm is derived from an absorption feature at the 4 sigma level of significance at the position of the R(0) line. This would imply a rotational temperature of not more than 22 K, with a more probable value of less than 16 K. Since total column density (3.2 x 10 to the 12th per sq cm) is found to be lower by a factor of approximately 4 than that which had been previously reported, substantial photo-dissociation of C2 is assumed.