SPECTROSCOPY OF THE 1 2-PI-U STATE OF NA-2(+)

We report here the first experimental observation of bound-bound transitions between the ground X 2Σg+ and excited 1 2Πu states of Na2+. The basis of our experiment is to study doubly excited Rydberg states of Na 2 by preparing a well-defined nd 1Λg singly excited Rydberg state of Na2 and then, by exciting the Na 2+ core with a tunable laser. In this paper, we show that the ionic transitions may be directly deduced from the doubly excited Rydberg states spectra [C. Bordas, J. L. Vialle, and M. Broyer (submitted)]. We demonstrate that this technique is one of the most powerful to study the excited states of diatomic ions which are not predissociated. A detailed spectroscopic analysis of the 1 2Πu state has been performed and the results are compared with the more recent ab initio and pseudo- (or model-) potential calculations. © 1990 American Institute of Physics.