Envelope Area and Electric Pulse Area Interference in Excitation of Quantum Systems by Few-Cycle Attosecond Light Pulses

In this letter, excitation of discrete levels in a quantum system is considered, when the duration of the driving pulse is changed from multicycle to ultrashort half-cycle regime. It is shown that, as the number of optical cycles decreases, the system passes from the periodic-driven regime to the “kick-driven” action. In both cases the effect depends on the pulse area. However for subcycle pulses the area is equal to the time integral of the field strength, whereas for multicycle pulses it is determined by the time integral of the pulse envelope. The interference of the envelope pulse area and the electric pulse area and its possible manifestations in experiments are discussed.