Skobeltsyn Institute of Nuclear Physics
Lomonosov Moscow State University

Some tunneling processes are described by unstable semiclassical solutions.
We develop a method to stabilize solutions by introducing an imaginary term
into the equations of motion. The new term is proportional to the
regularization parameter epsilon; the original unstable solutions, as well
as the correct value of the tunneling probability are recovered in the
limit epsilon->0. Our method is derived from the first principles and
generically applicable. We confirm the method by comparing the
semiclassical results for the tunneling probability with the exact
quantum-mechanical results.