26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Inelastic momentum transfer cross-sections from inelastic differential cross-sections for electron-impact excitation in Helium and in Argon

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral AIP | Atomic and Molecular Physics (ATMOP)

Description

For the rare-gases, the inelastic momentum transfer (IMT) cross-sections associated with electron-impact excitation and ionisation have not been studied extensively to date, although they are expected to play an important role in modelling electron transport in plasmas with improved accuracy. These cross-sections remain unavailable in most international databases. They are particularly important for characterising the behaviour of energetic plasma electrons (E=10-1000eV) generated in fast transient pulsed discharges. For plasma modelling purposes, the IMT cross-section is required to be defined as a smooth, continuous function of the electron energy starting at the excitation/ionisation thresholds, and this task is dependent on the availability of fully differential cross-sections (DCS). The requisite DCS’s for excitation have been calculated using the relativistic distorted wave (RDW) method which was originally developed in [1] and then applied to the excitation of the 6s[1/2]1 and 6s[3/2]1 states of Xenon between 30-80eV. The method was subsequently used to treat excitation processes in Argon, Krypton and Xenon up to 500eV. A modified version of the RDW method has been used here which allows for the ground and excited state wavefunctions to be determined in separate multi-configuration Dirac-Fock calculations, thereby giving a more accurate representation of both atomic states. The numerics of this new code have been modified so that it can accommodate incident energies greater than 2000eV (up to 5000eV), and incident electron orbital angular momentum greater than 100 au. The DCS’s from the RDW calculations will be directly compared to existing experimental and theoretical DCS data sets for selected electron energies up to E=500eV. Finally, state-specific IMT cross-sections for both helium and argon will be presented and compared to experimentally derived values, where available from the literature.

[1] T. Zuo, R.P. McEachran, A.D. Stauffer, J. Phys. B, 24 2853 (1991) and 25 3393 (1992)