We have tested the MP2 and CCSD(T) theory with various basis sets on the reaction energies and barrier heights of the two dissociation channels for the noble gas (Ng) molecules of the type XNgY: (a) XNgY -> X + Ng + Y, and (b) XNgY -> Ng + XY. We demonstrated that the MP2 method systematically overestimates the bond energies of XNgY molecules. We also obtained the theoretical half-lives of HArF and HCCArF as a function of temperature and energy barriers by calculating the unimolecular thermal rate constants of the two dissociation channels. (c) 2006 Elsevier B.V. All rights reserved.