2-COLOR STIMULATED RAMAN EFFECT OF PARA-HYDROGEN

A two-color stimulated Raman effect is investigated for para-hydrogen and is compared with that of ortho-hydrogen. A two-color (separated by 354 cm-1) dye-laser beam is focused into para-hydrogen that is pressurized to 3400 Torr. Many rotational and vibrational stimulated Raman lines are generated simultaneously. The conversion efficiency exceeds 10% for a rotationally shifted first Stokes line and 5% for a vibrationally shifted first Stokes line. A similar effect is reported for ortho-hydrogen with a two-color (separated by 587 cm-1) dye-laser beam, but para-hydrogen is more useful than ortho-hydrogen because of its closely separated lines. This result is ascribed to the transition J = 0 --> J = 2 for para-hydrogen, which is in contrast to J = 1 --> J = 3 for ortho-hydrogen.