TAO and MCZ acknowledge financial support of this work through an NSF predoctoral Fellowship (TAO) and through NSF Grant CHE9312651. The SCF/CI calculations were performed;
in part;
on an IBM SP computer obtained through a SUR 1996 grant from the IBM Corporation. PDR and PHH acknowledge financial support from MDA972-93-1-0030 from DARPA and F 49620-96-1-0026 from AFOSR. The assistance of Mr. Jay Lewis in preparing the manuscript is also acknowledged;