  The exciton ground state and excited state energies are calculated for a
model system of an infinitely long cylindrical wire. The effective Coulomb
potential between the electron and the hole is studied as function of the wire
radius. Within the adiabatic approximation, we obtain `exact' numerical results
for the effective exciton potential and the lowest exciton energy levels which
are fitted to simple analytical expressions. Furthermore, we investigated the
influence of a magnetic field parallel to the nanowire on the effective
potential and the exciton energy.
