LINE-SHAPE STUDIES IN HIGH-RESOLUTION STIMULATED RESONANCE RAMAN-SPECTROSCOPY AND APPLICATION TO ACCURATE DETERMINATIONS OF HYPERFINE SPLITTINGS IN I-2

We studied stimulated resonance Raman transitions between hyperfine su blevels of the ground electronic state X(1) Sigma(0+g)(v = 0, J = 13) of I-2. Resonances narrower than 10 kHz (HWHM) were obtained. A detail ed theoretical and experimental analysis of the line shape is presente d. The pressure broadening of Raman resonances was found to be 7 +/- 1 kHz/mTorr. The role of the beam divergence was investigated and shown to yield only a small broadening but some asymmetry of the lines. In the transit-time limit the theory predicts that the slow molecules sho uld play a dominant role, as in saturation spectroscopy. Our experimen tal conditions are very close to that regime, and we discuss the impro vements that should be made in order to reach it in future experiments . Finally, six hyperfine splittings of the ground state of I-2 were de termined with a 0.2-kHz accuracy. (C) 1996 Optical Society of America.