%0 Journal Article %T The Zeno and anti-Zeno effects on decay in dissipative quantum systems %A A. G. Kofman %A G. Kurizki %J Physics %D 1999 %I arXiv %X We point out that the quantum Zeno effect, i.e., inhibition of spontaneous decay by frequent measurements, is observable only in spectrally finite reservoirs, i.e., in cavities and waveguides, using a sequence of evolution-interrupting pulses or randomly-modulated CW fields. By contrast, such measurements can only accelerate decay in free space. %U http://arxiv.org/abs/quant-ph/9912077v1