Spontaneous nuclear excitation and the interpretation of delayed-coincidence Moessbauer effect data

It is shown that in spontaneous γ-ray decay, the probability per unit time w(ωsub(K) →, t) for emission of a γ ray with a specific energy ωsub(K) → behaves as an alternating probability current. When w(ωsub(K) →, t) is positive, this current goes from the excited to the ground state (spontaneous emission). When w(ωsub(K) →, t) is negative, this current goes in the opposite direction, i.e. w(ωsub(K) →, t) represents the probability that a photon is removed from the radiation field and the nucleus is reexcited. We refer to the latter effect as induced spontaneous excitation. The results of delayed-coincidence Moessbauer effect measurements are interpreted in terms of such induced spontaneous excitations. (orig.)