Post-exponential decay of the probability density of a quantum particle
leaving a trap can be reproduced accurately, except for interference
oscillations at the transition to the post-exponential regime, by means of an
ensemble of classical particles emitted with constant probability per unit time
and the same half-life as the quantum system. The energy distribution of the
ensemble is chosen to be identical to the quantum distribution, and the
classical point source is located at the scattering length of the corresponding
quantum system. A 1D example is provided to illustrate the general argument
