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 |MJ|. The splitting is proportional to |MJ| enabling resolution of the individual MJ peaks. Thus, this all-optical technique can be used to align nonpolar molecules. The line shapes are in excellent agreement with theory.