Angular Distribution and Polarization of the 3C and 3D Lines Following Electron-impact Excitation of Fe16+ Ions.

The electron-impact excitations from the ground state to the excited levels and as well as the subsequent radiative decays of neonlike Fe16+ ions have been investigated within the framework of the multiconfigurational Dirac–Fock method and the relativistic distorted-wave theory. Special attention has been paid to emission behaviors of the astrophysically relevant resonance 3C and intercombination 3D lines emitted in the radiative decays of Fe16+ ions. To this end, we calculate the angular distribution and linear polarization of both of the lines for a series of impact electron energies. It is found that the angular and polarization behaviors of the resonance 3C line are nearly the same as those of the intercombination 3D line. Nevertheless, the angular and polarization behaviors of both of the lines are found to be very sensitive to the impact electron energy, especially at low impact energies. Based on such a sensitivity, it is expected that high-precision angular and polarization measurements of the 3C and 3D lines could be served as a tool for revealing detailed information such as electron energy of relevant laboratory and astrophysical plasmas. [ABSTRACT FROM AUTHOR]