Using a longitudinally mode‐controlled transversely excited atmospheric CO2 laser, we studied the conversion characteristics of single‐, two‐, and multimode pump pulses in a para‐H2 Raman laser. In the small signal region, two‐ and multimode pump pulses showed higher Raman conversion efficiencies. In the saturation region, however, output energies pumped with single‐ and two‐mode pulses exceeded those pumped with multimode pulses. Consequently, the two‐mode pumping was the most efficient within the limit of pump energies used in the experiment. The results are explained in relation to the mode‐mixing effect for the correlated pump and Stokes beams. © 1995 American Institute of Physics.