  A classical solution to the Yang-Mills theory is given a new semiclassical
interpretation. The boundary value problem on a complex time contour which
arises from the semiclassical approximation to multiparticle scattering
amplitudes is reviewed and applied to the case of Yang- Mills theory. The
solution describes a classically for- bidden transition between states with a
large average number of particles in the limit $g\rightarrow 0$. It dominates a
transition probability with a semiclassical suppression factor equal to twice
the action of the well- known BPST instanton. Hence, it is relevant to the pro-
blem of high energy tunnelling. It describes transitions of unit topological
charge for an appropriate time contour. Therefore, it may have a direct
interpretation in terms of fermion number violating processes in electroweak
theory. The solution describes a transition between an initial state with
parametrically fewer particles than the final state. Thus, it may be relevant
to the study of semiclassical initial state corrections in the limit of a small
number of initial particles. The implications of these results for
multiparticle production in electroweak theory are also discussed.
