  We address the decay in open chaotic quantum systems and calculate
semiclassical corrections to the classical exponential decay. We confirm random
matrix predictions and, going beyond, calculate Ehrenfest time effects. To
support our results we perform extensive numerical simulations. Within our
approach we show that certain (previously unnoticed) pairs of interfering,
correlated classical trajectories are of vital importance. They also provide
the dynamical mechanism for related phenomena such as photo-ionization and
-dissociation, for which we compute cross section correlations. Moreover, these
orbits allow us to establish a semiclassical version of the continuity
equation.
