title: Strong-field induced XUV transmission and multiplet splitting in 4d(-1)6p core-excited Xe studied by femtosecond XUV transient absorption spectroscopy.
abstract: Light-induced coupling of core-excited states of Xe atoms is investigated by femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy with photon energies ranging from 50 eV to 72 eV. Coupling of the 4d(-1)((2)D(5/2))6p((2)P(3/2)) (65.1 eV) and 4d(-1)((2)D(3/2))6p((2)P(1/2)) (67.0 eV) core-excited states to nearby states by a strong infrared laser field leads to a threefold enhancement of XUV transmission. The transmission at 65.1 eV (67.0 eV) changes from 3.2 ± 0.4% (5.9 ± 0.5%) without the coupling laser to 9 ± 2% (22 ± 5%) at the maximum of the laser field. A strong-field induced broad XUV absorption feature between 60 eV and 65 eV is ascribed to splitting of the field-free absorption lines into multiple branches when the Rabi frequencies of the coupling transitions exceed the infrared laser frequency. This picture is supported by a comparison of the strong-field induced absorption spectrum with a numerical integration of the von Neumann equation for a few-level quantum system. The valence hole-alignment of strong-field ionized Xe is revisited, confirming the previously observed reduced alignment compared to theoretical predictions.
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Ming-Fu
authors.initials: MF
authors.lastname: Lin
authors.forename: Adrian N
authors.initials: AN
authors.lastname: Pfeiffer
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Neumark
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Leone
authors.forename: Oliver
authors.initials: O
authors.lastname: Gessner