  We analytically compute, in the first Born approximation for symmetric and
asymmetric coplanar geometries, the triple differential cross sections for
electron-impact ionization of hydrogen atom in the metastable 2S-state at both
low and high energies. The process is investigated by using the relativistic
Dirac-formalism and it is also shown that the nonrelativistic limit is
accurately reproduced when using low incident kinetic energies. At high
energies, relativistic and spin effects significantly affect the triple
differential cross sections. Our analytical approach which seems exact is
compared to some other results in the nonrelativistic regime for asymmetric
coplanar geometry. For this particular process and in the absence of any
experimental data and theoretical models at high energies, we are not in a
position to validate our model. We hope that the present study will provide
significant contribution to future experiments.
