In this project in the Physical Chemistry program of the Chemistry Division, Prof. Robert A. Bernheim of the Chemistry Department of the Pennsylvania State University will study the electronic state and spectroscopic properties of those states of the lithium diatomic molecule that exhibit double-minima or shelf-like structure in their potential curves. Under certain conditions the transition moments for shelf- and double-minimum states are predicted to be very large with strong and unusual dependence on internuclear separation. The lithium diatomic molecule is a testing ground for these and other predicted properties since it offers a rich variety of accessible spectroscopic states. This research deals with an experimental investigation of unusual spectroscopic and structural behaviors predicted theoretically for diatomic molecules. The results of these studies will provide new data that are necessary for the verification, and possible application to larger molecular systems , of the quantum theory of molecular states and behavior.