A technique to determine the thermal stability of uracil and uracil derivatives in a molecular beam

Uracil derivatives, especially synthesised for use in positron emission tomography studies, are heated to form a gas phase source and introduced into a vacuum system by seeding into a helium jet. Through time of flight mass spectroscopy, these uracil compounds are shown to have resisted any thermal dissociation during the heating phase of introduction into the jet. The successful introduction into a beam clearly demonstrates that dissociative electron attachment, or other scattering or spectroscopic studies, could be performed on these compounds with confidence that the parent molecule remains intact, at least at the temperatures considered in this study.