Quantum Zeno effect in the decay onto an unstable level

Under certain assumptions it is shown that the decay of level 2 of a three- level system onto level 1 is slowed down because of the further decay of le vel 1 onto level 0. It is argued that this phenomenon may be interpreted as a consequence of the quantum Zeno effect. The reason why this may be possi ble is that the second decay (or accompanying photon radiation) may he cons idered as a sign of the transition 2 --> 1 so that during the first transit ion the system is under continuous observation. (C) 1999 Published by Elsev ier Science B.V. All rights reserved.