  We make a brief review of the Kramers escape rate theory for the
probabilistic motion of a particle in a potential well U(x), and under the
influence of classical fluctuation forces. The Kramers theory is extended in
order to take into account the action of the thermal and zero-point random
electromagnetic fields on a charged particle. The result is physically relevant
because we get a non null escape rate over the potential barrier at low
temperatures (T -> 0). It is found that, even if the mean energy is much
smaller than the barrier height, the classical particle can escape from the
potential well due to the action of the zero-point fluctuating fields. These
stochastic effects can be used to give a classical interpretation to some
quantum tunneling phenomena. Relevant experimental data are used to illustrate
the theoretical results.
