The dynamics of a THz Rydberg wavepacket

An optically excited Rydberg wavepacket can be generated by exciting the el ectron from a low-lying state to a coherent superposition of high-lying sta tes with a short broadband optical pulse. A special kind of Rydberg wavepac ket is generated in the case of a interaction of a weak THz half cycle puls e with a stationary Rydberg state, called the THz; wavepacket. This THz wav epacket is a coherent superposition of the initial Rydberg state and its ne ighbouring states. We have investigated the time evolution of THz wavepacke ts by measuring the impact of two in time delayed half cycle pulses (approx imate to 200 V cm(-1)) on the population of a stationary (n = 40) Rydberg s tate in rubidium. The first half cycle pulse creates the THz wavepacket and the second half cycle pulse probes the dynamics of the THz wavepacket. We support our experimental data by numerically solving the Schrodinger equati on and with a semi-classical picture. Whereas an optically excited wavepack et is initially localized, a THz wavepacket is initially delocalized and be comes localized after half a revival time.