536 research outputs found
The Multi-Configurational Hartree-Fock close-coupling ansatz: application to Argon photoionization cross section and delays
We present a robust, ab initio method for addressing atom-light interactions
and apply it to photoionization of argon. We use a close-coupling ansatz
constructed on a multi-configurational Hartree-Fock description of localized
states and B-spline expansions of the electron radial wave functions. In this
implementation, the general many-electron problem can be tackled thanks to the
use of the ATSP2K libraries [CPC 176 (2007) 559]. In the present contribution,
we combine this method with exterior complex scaling, thereby allowing for the
computation of the complex partial amplitudes that encode the whole dynamics of
the photoionization process. The method is validated on the 3s3p6np series of
resonances converging to the 3s extraction. Then, it is used for computing the
energy dependent differential atomic delay between 3p and 3s photoemission, and
agreement is found with the measurements of Gu\'enot et al. [PRA 85 (2012)
053424]. The effect of the presence of resonances in the one-photon spectrum on
photoionization delay measurements is studied.Comment: 15 pages, 8 figures, 4 table
Multi-polariton control in attosecond transient absorption of autoionizing states
Tunable attosecond transient absorption spectroscopy is an ideal tool for
studying and manipulating autoionization dynamics in the continuum. We
investigate near-resonant two-photon couplings between the bright 3s^-1 4p and
dark 3s^-1 4f autoionizing states of argon that lead to Autler-Townes like
interactions, forming entangled light-matter states, or polaritons. We observe
that one-photon couplings with intermediate dark states play an important role
in this interaction, leading to the formation of multiple polaritonic branches
whose energies exhibit avoided crossings as a function of the dressing-laser
frequency. Our experimental measurements and theoretical essential-state
simulations show good agreement and reveal how the delay, frequency, and
intensity of the dressing pulse govern the properties of autoionizing polariton
multiplets. These results demonstrate new pathways for quantum control of
autoionizing states with optical fields.Comment: 8 pages, 6 figure
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