Data on excitation of rare gases is important in the study of plasma displays, lighting and lasers.
From literature, both relativistic and non-relativistic computations performed on electron impact
excitation of low-lying states of rare gases often fail to give satisfactory agreement with available
experimental data mostly at low impact energies and at intermediate scattering angles. With this
in view, in the present study, we have applied relativistic effects in a fully-relativistic distortedwave approach to excitation of the lowest lying resonance states of argon, krypton and xenon
gases, by modifying the electron-atom interaction distortion potential in such a way that the
complex part, the absorption potential, and the real part, which includes an energy dependent
polarization potential, exchange and electrostatic potentials, form the complex distortion
potential used in calculating radial wavefunctions. The atomic wavefunctions are constructed in
the multi-configuration Dirac-Fock approach by modifying the general-purpose relativistic
atomic structure code GRASP for numerical procedures. In this study, the WKB approximation
is used to compute the free continuum electron wavefunctions which are then used in computing
scattering cross sections and angular parameters using our program RDWBA1. Present results
from this study predict that use of a complex distortion potential in the relativistic approach to
excitation of argon, krypton and xenon generally lowers integral cross sections as impact
energies of the incident electron increases, compared to those obtained using real distortion
potentials only. For argon, the effect of the absorption potential, which accounts for loss of flux
into other open scattering channels is more visible at electron impact energies above 50 eV,
while for krypton, absorption becomes more dominant above 100 eV. For xenon, which is the
heaviest of the three, absorption in the distortion potential generally has minimal effect on cross
sections at impact energies below 50 eV then significantly improves these results when
compared with experiments as kinetic energy of the electron increases. Furthermore, for all the
rare gases under investigation, it is the energy dependent polarization potential adopted, that
plays a major role in improving shapes of cross-sections at low and near threshold impact
energies, where available distorted-wave methods fail to give satisfactory results when compared
to experiments. We have also obtained angular correlation parameters lambda to predict the
magnetic sublevel responsible for most excitations, and Stokes parameters to predict the
polarization of the emitted photon during atomic decay. Cross section results obtained from this
study are in good agreement with experiments at all impact energies under investigation,
therefore it will be interesting to see how these cross sections vary when this present approach is
used to investigate excitation of the metastable states of rare gases with both electron and
positron impact.