Post--Big Bang Processing of the Primordial Elements

We explore the Gnedin-Ostriker suggestion that a post-big bang photodissociation process may modify the primordial abundances of the light elements. We consider several specific models and discuss the general features that are necessary (but not necessarily sufficient) to make the model work. We find that with any significant processing, the final D and {sup 3}He abundances, which are independent of their initial standard big bang nucleosynthesis (SBBN) values, rise quickly to a level several orders of magnitude above the observationally inferred primordial values. Solutions for specific models show that the only initial abundances that can be photoprocessed into agreement with observations are those that undergo virtually no processing and are already in agreement with observation. Thus it is unlikely that this model can work for any nontrivial case unless an artificial density and/or photon distribution is invoked. {copyright} {ital 1996 The American Astronomical Society.}