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Sensitivity of nonlinear photoionization to resonance substructure in collective excitation.

Mazza T, Karamatskou A, Ilchen M, Bakhtiarzadeh S, Rafipoor AJ, O'Keeffe P, Kelly TJ, Walsh N, Costello JT, Meyer M, Santra R - Nat Commun (2015)

Bottom Line: Resonant photoionization of atomic xenon was chosen as a case study.The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance.Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources.

View Article: PubMed Central - PubMed

Affiliation: European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg, Germany.

ABSTRACT
Collective behaviour is a characteristic feature in many-body systems, important for developments in fields such as magnetism, superconductivity, photonics and electronics. Recently, there has been increasing interest in the optically nonlinear response of collective excitations. Here we demonstrate how the nonlinear interaction of a many-body system with intense XUV radiation can be used as an effective probe for characterizing otherwise unresolved features of its collective response. Resonant photoionization of atomic xenon was chosen as a case study. The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance. Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources.

No MeSH data available.


Schematic representation of the ionization processes and associated models.(a) 1-photon ionization process; (b) 2-photon ionization process; (c) 1- and 2-photon processes according to the reduced model, only including interaction of the emitted electron with the hole from which it is excited; (d) 1- and 2-photon processes according to the full model, accounting for electron–hole interaction in all channels open to ionization.
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f1: Schematic representation of the ionization processes and associated models.(a) 1-photon ionization process; (b) 2-photon ionization process; (c) 1- and 2-photon processes according to the reduced model, only including interaction of the emitted electron with the hole from which it is excited; (d) 1- and 2-photon processes according to the full model, accounting for electron–hole interaction in all channels open to ionization.

Mentions: Employing nonlinear electron spectroscopy, namely through the study of xenon 2-photon ionization, we demonstrate here that the nonlinear process unveils otherwise unresolved aspects of the collective behaviour of the system. Due to the photon energy selected, the 2-photon process occurs through the giant resonance as an intermediate step (Fig. 1). We show, however, that a model assuming a single intermediate state cannot describe our results. Instead, the resonance feature in the predicted energy dependence of the 2-photon process and its shape strongly suggest that more than one resonance state underlie the giant resonance22; although these states are unresolved in the linear ionization of xenon, 2-photon ionization turns out to be a sensitive process for their observation.


Sensitivity of nonlinear photoionization to resonance substructure in collective excitation.

Mazza T, Karamatskou A, Ilchen M, Bakhtiarzadeh S, Rafipoor AJ, O'Keeffe P, Kelly TJ, Walsh N, Costello JT, Meyer M, Santra R - Nat Commun (2015)

Schematic representation of the ionization processes and associated models.(a) 1-photon ionization process; (b) 2-photon ionization process; (c) 1- and 2-photon processes according to the reduced model, only including interaction of the emitted electron with the hole from which it is excited; (d) 1- and 2-photon processes according to the full model, accounting for electron–hole interaction in all channels open to ionization.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403373&req=5

f1: Schematic representation of the ionization processes and associated models.(a) 1-photon ionization process; (b) 2-photon ionization process; (c) 1- and 2-photon processes according to the reduced model, only including interaction of the emitted electron with the hole from which it is excited; (d) 1- and 2-photon processes according to the full model, accounting for electron–hole interaction in all channels open to ionization.
Mentions: Employing nonlinear electron spectroscopy, namely through the study of xenon 2-photon ionization, we demonstrate here that the nonlinear process unveils otherwise unresolved aspects of the collective behaviour of the system. Due to the photon energy selected, the 2-photon process occurs through the giant resonance as an intermediate step (Fig. 1). We show, however, that a model assuming a single intermediate state cannot describe our results. Instead, the resonance feature in the predicted energy dependence of the 2-photon process and its shape strongly suggest that more than one resonance state underlie the giant resonance22; although these states are unresolved in the linear ionization of xenon, 2-photon ionization turns out to be a sensitive process for their observation.

Bottom Line: Resonant photoionization of atomic xenon was chosen as a case study.The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance.Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources.

View Article: PubMed Central - PubMed

Affiliation: European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg, Germany.

ABSTRACT
Collective behaviour is a characteristic feature in many-body systems, important for developments in fields such as magnetism, superconductivity, photonics and electronics. Recently, there has been increasing interest in the optically nonlinear response of collective excitations. Here we demonstrate how the nonlinear interaction of a many-body system with intense XUV radiation can be used as an effective probe for characterizing otherwise unresolved features of its collective response. Resonant photoionization of atomic xenon was chosen as a case study. The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance. Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources.

No MeSH data available.