Electron impact coherence parameters for superelastic transitions terminating on the (…6s6p¹P₁) 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.

Low energy super-elastic scattering studies of calcium over the complete angular range using a magnetic angle changing device

“…The disadvantage of the super-elastic technique is that the laser frequency must be resonant with an atomic transition which is coupled to the ground state of the target. Present day tuneable high-resolution laser systems can only access a limited number of atoms and so this restricts the technique to these targets [7][8][9][10][11][12][13][14][15][16][17][18]. Experiments have almost exclusively been conducted from atoms in an excited P-state due to this restriction, although there has been one set of data exciting the D-state of sodium from a laser prepared P-state using electrons [10].…”

“…Equation (3) then reduces to that for a conventional superelastic experiment (e.g. as adopted in [12][13][14]18]).…”

Differential cross sections for electron impact excitation out of the (…6s6p1P1) state of barium

“…. 6s6p 1 P 1 ), for higher lying levels, X, have been measured and are, generally, well described by this theoretical approach [3,4].…”

Differential cross sections and electron impact coherence parameters for elastic electron scattering from laser-excited138Ba

“…The change from RHC to LHC laser light leads to a change of sign of the T a 10 ( j) in the second term in the right-handside of (18). For scattering from the laser prepared P state we evaluated the DCS(±) and then use (4) and ( 5) to calculate the PDCS and P 3 Stokes parameter.…”