No abstract

A detailed study using fully relativistic distorted wave theory for electron impact excitation of Zn-like through Co-like tungsten ions is presented in a wide range of incident electron energies up to 50 keV. We have considered electron impact excitations, namely 3d–4p and 3d–nf (n = 4–8) transitions from the M-shell of the ground state in the Zn-like W44+, Cu-like W45+, Ni-like W46+ and Co-like W47+ ions. We report excitation cross sections for these dipole allowed transitions considered in all the four ions along with the linear polarization of the photon emissions due to the decay of the excited anisotropic states to the ground state. We also provide the analytic fits to our calculated cross sections for plasma application purposes.

We have measured and calculated differential cross sections and the P 3 collision Stokes parameter for elastic electron scattering from the laser-excited (. . . 6s6p 1 P 1 ) and cascade-populated (. . . 6s5d 3 D 1,2 ) levels of barium at 5, 10, and 20 eV impact energy. Measurements were performed using a crossed-beam apparatus, where excited-state atomic targets were prepared with resonant laser radiation incident on the electron-atom interaction region. Calculations were performed in the convergent close-coupling (CCC), relativistic CCC, and optical-model potential approximations. We present measured and calculated partial differential cross sections, which relate to differential cross sections and electron impact coherence parameters through the target state anisotropy introduced by the laser geometry.

Electron impact excitations from ground state L shell viz. n = 2 → n = 3 transitions in Mg-like W62+, Na-like W63+, Ne-like W64+, F-like W65+ and O-like W66+ ions have been considered. A fully relativistic distorted wave (RDW) theory has been used to calculate the excitation cross-sections for an electric and magnetic dipole, as well as for the quadrupole transitions for these ions, which were observed recently in the measurements taken from an electron-beam-ion trap (EBIT-I) at the Livermore laboratory. We have performed calculations in the electron impact energy range from a threshold excitation energy of up to 60 keV. Our results, where possible, have been compared with the few previous theoretical calculations that are available. Analytic fits to our calculated excitation cross-sections have also been done for plasma modeling purposes. Our calculated cross-sections have been further employed to obtain the linear polarization of the photon emissions for dipole-allowed transitions due to the decay of the electron impact excited anisotropic states to the ground state for all five of the tungsten ions that are considered in the present work.