Electron impact coherence parameters for superelastic transitions terminating on the (…6s6p 1P1) level of the barium atom

Abstract

We have investigated inelastic electron scattering from the laser-excited (…6s6p 1P1) state of barium at 20 eV incident electron energy and scattering angles of 5.5°, 9°, 13° and 16°. Laser excitation with linearly polarized light allowed us to extract P1 and P2 Stokes parameters and the λ parameter for the time-inverse related de-excitations X → (…6s6p 1P1) with X = (…6s7p 1P1), (…6s6d 1D2), (…6s7s 1S0), (…5d2 3P2) and (…5d2 1D2 + …5d6p 1D2). In combination with previously measured values of the P3 Stokes parameter (Johnson P V, Zetner P W, Fursa D and Bray I 2002 Phys. Rev. A 66 22707), we are able to present the set of natural parameters {γ, P+lin, h, P+} for these de-excitations. Comparison of the experimental results with theoretical results calculated in the convergent close coupling formalism is made.