  Continuum states of the Dirac equation are calculated numerically for the
electrostatic field generated by the charge distribution of an atomic nucleus.
The behavior of the wave functions of an incoming electron with a given
asymptotic momentum in the nuclear region is discussed in detail and the
results are compared to different approximations used in the data analysis for
quasielastic electron scattering off medium and highly charged nuclei. It is
found that most of the approximations provide an accurate description of the
electron wave functions in the range of electron energies above 100 MeV
typically used in experiments for quasielastic electron scattering off nuclei
only near the center of the nucleus. It is therefore necessary that the
properties of exact wave functions are investigated in detail in order to
obtain reliable results in the data analysis of quasielastic (e,e'p) knockout
reactions or inclusive quasielastic (e,e') scattering. Detailed arguments are
given that the effective momentum approximation with a fitted potential
parameter is a viable method for a simplified treatment of Coulomb corrections
for certain kinematical regions used in experiments. Numerical calculations
performed within the framework of the single particle shell model for nucleons
lead to the conclusion that our results are incompatible with calculations
performed about a decade ago, where exact electron wave functions were used in
order to calculate Coulomb corrections in distorted wave Born approximation. A
discussion of the exact solutions of the Dirac equation for free electrons in a
Coulomb field generated by a point-like charge and some details relevant for
the numerical calculations are given in the appendix.
