ELECTRON-SCATTERING FROM LASER-EXCITED BARIUM - STUDIES OF THE (...6S5D(1)D(2)) TO (...6S6P(1)P(1)) TRANSITION

We report on measurements of the lambda parameter and absolute differe ntial cross section for electron-impact excitation of the (...6s6p P-1 (1)) state in barium from the metastable, isotropically populated (... 6s5d D-1(2)) level at 20 eV impact energy. The determination of these scattering parameters was facilitated by the utilization of a novel la ser excitation geometry and measurement scheme. Along with our previou s measurements of electron-impact coherence parameters for this transi tion we now have available a complete set of the five parameters which characterize the excitation of a P state by the scattering of unpolar ized electrons from an isotropic (metastable) D level. Comparison of m easured values with recent calculations carried out in the unitarized distorted-wave approximation reveals good agreement.