Autler-Townes splitting in molecular lithium: Prospects for all-optical alignment of nonpolar molecules

We demonstrate Autler-Townes (AT) splitting in molecular lithium using cw triple resonance spectroscopy. The pump and tunable probe lasers create sub-Doppler double resonance excitation of an upper rovibrational level. The line shape is split in the presence of a third, coupling laser. The AT line shape consists of the superposition of several narrower twin peaks, one for each \M-J\. The splitting is proportional to \M-J\ enabling resolution of the individual M-J peaks. Thus, this all-optical technique can be used to align nonpolar molecules. The line shapes are in excellent agreement with theory.