Identification of excited states in Na2 by two-step polarization labeling

In two-step polarization labeling, as in polarization labeling, a polarized pump laser is tuned to a molecular transition. This produces an optical anisotropy in the upper and lower levels of the pump transition. A linearly polarized probe laser will experience a change in polarization when it interacts with these oriented levels of the molecule. Probe delays of several nanoseconds distinguish lower level depolarization from upper level depolarization. The technique has been applied to Na₂ to identify three new excited states. Preliminary values of some of the molecular constants are presented.