B Baumgartner
Interchannel Resonances at a Threshold
(32K, LaTeX)
ABSTRACT. Fermi's Golden Rule, the perturbation theoretic formula for calculating
the half width of a resonance, is not applicable to the case of a
transition from a bound state into an open channel, when the energy of
the bound state is exactly at the threshold of the continuum. We study
solvable models of this phenomenon. The exact results coincide in
leading order with the formulas found by modifying Fermi's Golden Rule.