Probe-field spectra of N-scheme in strong inhomogeneous fields

Measurements of probe-field spectra in an N-configuration of rovibrational states of sodium dimers with two strong fields in opposite transitions are reported. From two to four peaks in the spectrum are observed, while theory has predicted up to six peaks. The discrepancy is explained by the absorpt ion of the strong fields. A variation of the Rabi frequencies along the med ium shifts the peaks and results in broadening of individual peaks and a re duction of the number of resolved components. A qualitative agreement with experiment is demonstrated. Additional mechanisms of broadening due to coll isions and degeneracy of molecular states with large angular momentum are d iscussed.