Pump-probe spectroscopy of the sodium D-1 line and the question of recoil-induced gratings in hot vapors

We present experimental and numerical results concerning the absorption pro perties of sodium vapor at moderate densities strongly driven by a pump fie ld in the presence of a very low-intensity probe field and develop a three- level model for saturated absorption to better describe the hyperfine struc ture of the D-1 line. We show that this model is sufficient to explain our experimental results, and therefore conclude that recoil-induced gratings, in this configuration, are expected at higher pump and probe intensities. ( C) 1999 Elsevier Science B.V. All rights reserved.