Manipulation of spatial distribution of state-selected excited molecules using a combination of the Autler-Townes effect  under conditions of optical pumping and interference caused by presence of light-induced crossings of the molecular states is studied. In the experiment, a supersonic molecular beam is crossed by two cw laser beams coupled in an open three-level ladder scheme. Lasers are focused in such a way that strong and short laser field pulse couples the two lower levels, and weak and long laser field pulse couples the two upper levels. Hence, the excitation spectrum of the upper level is strongly affected by the dynamics of optical pumping on the lower transition.
Fig. 1. Calculated fluorescence signal from the upper level of a three-level ladder system, excited by two co- and counter-propagating lasers fields.
Detailed numerical calculations based on the dressed-state picture  show that such an arrangement of both laser fields can be used to vary the spatial distribution of highly excited molecules, which can be precisely controlled by varying laser frequencies and intensities. When the frequencies of both laser fields are fixed, the excitation of the upper level can take place at two distinct spatial locations (Landau-Zener transition regions), where the second laser field is resonant with one of the dressed states associated with interaction with the laser field in the first excitation step. This leads to two alternative excitation pathways, whereby the probability amplitude of the upper level at the second Landau-Zener transition region is determined by their constructive or destructive interference.
Calculations and experimental results for the case of excitation high lying states of Na2 are presented. Simulations show (see Fig. 1) that interference fringes in the excitation spectrum of the upper level can be resolved when counter-propagating laser beams are used, which allows elimination of the residual Doppler width.