Ion irradiation and extended CO emission in cometary comae

New laboratory results on the synthesis of carbon suboxides by ion irradiation of frozen CO (and of CO:O-2 and CO:N-2 mixtures) are presented. Some recently published results on irradiation of CO2 (and CO2:H2O mixtures), producing, among other species, carbonic acid are summarized. It is suggested that some of the newly formed compounds could contribute to explaining the observed extended emission of CO in cometary comae. Those species being less volatile could in fact be sublimated far from the nucleus and, once dissociated, be potential sources of CO molecules. (C) 1997 Elsevier Science Ltd.