High-resolution coherent spectroscopy: linewidth reduction by recurrent excitation

Summary form only given. Spectral narrowing by recurrent use of free-decay signal in magnetic resonance has been proposed and demonstrated in the ground state of Rb atoms. In the present report we apply this technique to the measurement of the hyperfine frequency in the excited state. This is a sublevel spectroscopy with recurrent excitation where the atomic response is iteratively used as the next excitation. The hyperfine spectra of the excited state /sup 2/P/sub 3/2/ of the D/sub 2/ transition in /sup 85/Rb atoms, the line widths of which are much narrower than the natural width, were observed and the hyperfine constants of the excited state were determined precisely.