title: Subcycle ac stark shift of helium excited states probed with isolated attosecond pulses.
abstract: Recent advances in attosecond science have relied upon the nearly instantaneous response of free electrons to an external field. However, it is still not clear whether bound electrons are able to rearrange on sublaser cycle time scales. Here, we probe the optical Stark shifts induced by a few-cycle near infrared laser field in helium bound states using isolated attosecond pulses in a transient absorption scheme and uncover a subcycle laser-induced energy level shift of the laser-dressed 1s3p state.
authors.affiliation: CREOL, Orlando, Florida 32816, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Chini
authors.forename: Baozhen
authors.initials: B
authors.lastname: Zhao
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.forename: Yan
authors.initials: Y
authors.lastname: Cheng
authors.forename: S X
authors.initials: SX
authors.lastname: Hu
authors.forename: Zenghu
authors.initials: Z
authors.lastname: Chang