Laser-based optical pumping of an extended path length supersonic expansion at concentrations in excess of 10(15) cm(-3) elucidates the first example of a chemically induced Raman pumping process involving sodium-halogen atom reactions. The chemically induced Raman process, which involves the scattering of Na D-line photons by Na-2 and is characterized by a large similar to 4 cm(-1) scattering line width, is shown to be associated with the presence of excited Na (3P) atoms and does not correlate with laser photon flux alone. The process is inefficient or nonexistent for laser excitation wavelength shifts Delta lambda greater than or equal to 0.5 nm from the Na D-lines and would appear to correlate with a significant Na (3P)-Na-2 interaction in the form of a weakly bound exciplex.