State-selective preparation of Ar2+ and Kr2+ by resonantly enhanced two-photon double ionization via intermediate Rydberg states using high-order harmonics

摘要

Simultaneous two-electron emission processes of Ar induced by high-order harmonics of near-infrared femtosecond laser pulses were investigated by coincidence photoelectron spectroscopy. Two-photon double ionization processes via the 3s3p(6)np (n similar to 25) intermediate resonances of Ar were observed, which selectively created the 3s3p(51)P state of Ar2+. The similar double ionization processes were also observed in Kr. The selective creation indicates that the core electron configuration of the doubly ionized state tends to be the same as that of the intermediate state and that the emitted two electrons tend to form the singlet state.