  Frequent Measurements on an unstable particle located at observable initial
state freeze the particle on this state, known as quantum Zeno effect [1-14].
Measurements on an observable subspace further open the prelude of quantum Zeno
dynamics [15-17]. These phenomena affect the results of quantum measurement
that has been widely used in quantum information and quantum computation
[18-21]. However, this common argument is insufficient when the initial state
is coupled with a continuum reservoir. In such an irreversible system,
intrinsic decay property destroys the frozen behavior. Although it has been
proven that the decay rate of the initial state will be affected by
measurements [7], the knowledge of detailed mechanisms for this
measurement-dependent decay is still limited. In this work, we found based on
three-subsystem perturbation theory that the indirect correlation between a
continuum reservoir and a measurement apparatus through the interaction with a
quantum system causes a Rabi-like inter-modulation among these subsystems. The
indirect correlation effect from this combination drives the system into
quantum Zeno and reactivation regions, which are dependent upon the Rabi
strength, pulse duty, and its repetition rate. We also found that the dynamical
changes of decay rate are quite different in continuous and pulsed
measurements, and, thus, significantly affect the dynamics of the system.
