Suppression of a Recoil Component in Nonlinear Doppler-Free Spectroscopy

A new method to suppress one of the two recoil components in saturation and Ramsey spectroscopy is presented. It is applied to the calcium intercombination line ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}-{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ ($\lambda \cong 675$ nm) by optical pumping of the calcium atoms from the metastable ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ state through the ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ state into the ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$ or the ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ states. The suppression of the low-frequency recoil component could be deduced in saturated absorption from a narrowing and shift of the Lamb dip as well as observed directly in Ramsey fringe spectroscopy when the recoil doublet was resovled.