  We consider the quantum tunneling phenomenon in a well-behaved triple-well
potential. As required by the semiclassical approximation we take into account
the quadratic fluctuations over the instanton which represents as usual the
localised finite-action solution of the euclidean equation of motion. The
determinants of the quadratic differential operators at issue are evaluated by
means of the Gelfang-Yaglom method. In doing so the explicit computation of the
conventional ratio of determinants takes as reference the harmonic oscillator
whose frequency is the average of the individual frequencies derived from the
non-equivalent minima of the potential. Eventually the physical effects of the
multi-instanton configurations are included in this approach. As a matter of
fact we obtain information about the energies of the ground-state and the two
first excited levels of the discrete spectrum at issue.
