  The possibility to observe quantum Zeno and anti-Zeno scenarios for
atom-diatom reactive collisions is investigated for two diferent processes
(F+HD and H+O_2) by means of time-dependent wave packet propagations. A novel
approach is proposed in which the survival probabilities investigated are those
obtained when the initial state is redefined after time intervals tau at which
measurements are performed on the system. The comparison with the actual
probability for the unperturbed system reveals the existence of a regime in
which the decay from the initial state appears to be inhibited (the quantum
Zeno effect) or accelerated (the anti-Zeno effect). In contrast with preceding
interpretations, given that the time-evolving wave packet is not affected at
any time ("flying arrow"), the present procedure does not require to invoke to
counterintuitive hindered evolutions ("stopping arrow") to explain the results.
On the contrary the consecutive update of the reference state of the system
solves the apparent modern version of Zeno's paradox.
