Differential cross sections for electron-impact excitation of laser-excited ~(174)Yb (... 6s6p ~3P_1)

摘要

We have measured and calculated electron-impact excitation cross sections from the laser-excited Yb (... 6s6p ~3P~1) level to the higher-lying Yb (... 6s6p ~1P_1), (... 6s5d ~3D_(1,2,3)) and (... 6s7s ~3S_1) levels at 20 eV impact energy. Measurements were performed using a crossed-beam apparatus, with resonant laser radiation incident on the electron-atom interaction region, providing excited-state atomic targets. Calculations were performed in the relativistic convergent close-coupling (RCCC), convergent close-coupling (CCC), and relativistic distorted-wave (RDW) approximations. We present measured and calculated partial differential cross sections (PDCS), which relate to differential cross sections and electron-impact coherence parameters through the target state anisotropy introduced by the laser geometry. Using theoretical predictions of the h electron-impact coherence parameter, we present the differential cross section for the ~3P_1- ~3S_1 excitation.