Phase and rise-time dependence using rf pulses in multiphoton processes

With this experiment we demonstrate that excitation of a two-state system with radio-frequency fields differing in phase by 90^∘{} produces nonintuitively different results, even for very long pulses. In addition, we show how the phase dependence of the transition probability of long pulses can be easily understood by using the single cycle time propagator. Finally, we have found surprising results for real pulses in the strong-field regime, i.e., pulses having appreciable rise and fall times.