Oscillator Strength Measurements of Even-Parity Autoionizing Resonances by Combined Synchrotron-Radiation-Laser Excitation

We have obtained oscillator strengths for transitions between a laser-excited initial state and autoionizing final states. In the case of sodium, a laser was used to populate the $3p$ initial state, and synchrotron radiation was used to excite the autoionizing resonances. These transitions are of the type $2p^{6}3p{}_{}{}^2{}_{}{}^{}P\to 2p^5\left({}_{}{}^2{}_{}{}^{}P\right)3s3p\left({}_{}{}^{1,3}{}_{}{}^{}P\right){}_{}{}^{2,4}{}_{}{}^{}S,{}_{}{}^{2,4}{}_{}{}^{}P,{}_{}{}^{2,4}{}_{}{}^{}D$; they decay to $2p^6{}_{}{}^1{}_{}{}^{}S+e$. The sum of the oscillator strengths for all the observed transitions between the $2p^{6}3p$ initial-state and the $2p^{5}3s3p$ final-state configurations was found to be equal to 0.22(4).