Bandwidth-induced reversal of asymmetry in optical-double-resonance amplitudes

Optical-double-resonance measurements using ionization detection have been carried out in the $3S_{\frac{1}{2}}-3P_{\frac{1}{2}}-4D$ atomic-sodium system. Asymmetries observed in production of $4D$ atoms from the two components of the Stark-split $3P_{\frac{1}{2}}$ state are found to be controlled by the far, very weak wings of the 17-MHz full-width-at-half-maximum laser line which is used to drive the $3S_{\frac{1}{2}}-3P_{\frac{1}{2}}$ transition at detunings in the range 0-70 GHz. Suppression of the wings with a Fabry-Perot filter causes a pronounced reversal of the asymmetry.