Quantum Zeno-like effect and spectra of particles in cascade transition

Shrodinger equation for two-step spontaneous cascade transition in a three- level quantum system is solved by means of Markovian approximation for non- Markovian integro-differential evolution equations for amplitudes of states . It is shown that both decay constant and radiation shift of initial level are affected by instability of intermediate level of the cascade. These ph e nomena are interpreted as the different manifestations of quantum Zeno-li ke effect. The spectra of particles emitted during the cascade transition a re calculated in the general case and, in particular, for an unusual sit-na tion when the initial state is lower than the intermediate one. It is shown that the spectra of particles do not have a peak-like shape in the latter case. (C) 2000 Published by Elsevier Science B.V. All rights reserved.