THE CHEMISTRY OF DEUTERIUM IN HOT MOLECULAR CORES

This paper presents the results of a model of the chemistry of deuteri um-bearing molecules in hot molecular cores. It is found that because hydrogen- and deuterium-bearing molecules are destroyed by the same re actions at about the same rates, the initial fractionation present in ice mantles persists for over 10(4) yr. This is the case for a wide ra nge of physical conditions, so it is safe to infer the fractionation o n grain surfaces from observations of deuterated molecules in hot core s. The implications of the observed abundances of deuterium-bearing sp ecies in Orion are then discussed.