For a one-dimensional atom, we derive an exact analytical expression for the uncertainty product of a Rydberg wave packet (WP) produced by the impact of two time-delayed half-cycle pulses (HCPs) and use the result to study the problems of its (WP's) phase-space localization. We also investigate how to effectively use the second HCP to increase the atomic ionization probability. The time delay (t1) between the two HCPs plays a crucial role in both cases. The values of t1 can be chosen for the second HCP to kick the WP when the latter is near the inner or outer turning point. We found that long-lived localized states are produced by the impact of the second HCP only when the WP is near the inner turning point. In the same situation, if the electron is kicked away from the nucleus, the atomic ionization probability tends to a maximum.