It is shown that the production of electrons by the laser-gas
interaction, described in a previous paper , at a given position
in the interelectrode gap of a DC electrical discharge, is responsible
for a transient current associated to the displacement of the
running point on the current-voltage characteristic. A theoretical
model of the laser-induced current impulse, in good agreement
with experiments, is proposed in the case of homogeneous field.
Some macroscopic coefficients, like first and second ionization
coefficients, or electrons and ions velocities, are examined.
The estimated values are compared with ones found in the literature.
The theory in homogeneous field, well supported by the experiments,
allows to give a qualitative interpretation to the laser-induced
current impulse in inhomogeneous field (point-to-plane geometry).
As a result, depending on the location of the running point on
the I−V characteristic and on the laser energy available for
photon-ionization, it is shown that the laser-gas interaction
is an accurate and effective technique for the investigation
of the fundamental processes involved in each electrical state
of the discharge (townsend discharge, self-sustained discharge,
glow discharge) and in the transition from a state to another
(for example, avalanche-to-streamer transition).