  The mechanisms for population inversion among the excited states of He I and
Ne I in regenerative sooting discharges have been investigated as a function of
the geometry and the physical parameters of the graphite hollow cathode
sources. The effect of the state of sooting of the hollow cathode, the gas
pressure and the role of the cycling of the discharge current idis on the
population inversion of the excited He I and Ne I levels have been
investigated.
