Abstract: We have explored how the correlation between the decay rate of a molecular negative ion and its inter-nuclear coordinates influences the desorption yield produced by electron attachment to a shape resonance of an adsorbed diatomic molecule. An analytic model of resonance-assisted desorption is modified to treat the dynamical evolution of the decay rate. Using this model we demonstrate that the equilibrium lifetime, which is commonly measured in short-time dynamical measurements such as high-resolution electron energy loss spectroscopy or inverse photoemission spectroscopy, overestimates the decay rate of those negative ions which live sufficiently long to induce desorption.