Efficient generation of Stokes lines has been obtained in H2, CH4, N2, and O2 by 10 ps, 300 Hz, 193 nm laser pulses. A 60% energy conversion efficiency was recorded for the first Stokes of H2 and 40% in CH4. For the pressure range 1-30 atm the conversion efficiency did not change with pump pulse repetition rate up to 300 Hz. The higher order Stokes observed were generated mainly by means of four wave mixing.
