Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

Jordan, Inga; Huppert, Martin; Brown, Matthew A.; Bokhoven, Jeroen A. van; Wörner, Hans Jakob

doi:10.1063/1.4938175

Cited by 49 publications

(51 citation statements)

References 42 publications

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“…In conclusion, we have reported the measurement and theoretical interpretation of attosecond delays in the photoionization of molecules. This development makes molecular systems in the gas, liquid [17] and solid phases accessible to attosecond interferometry. The measured delays are found to be remarkably large in N 2 O, which is shown to be a consequence of transient trapping of the photoelectron in shape resonances.…”

Section: (7)mentioning

confidence: 99%

Attosecond Delays in Molecular Photoionization

et al. 2016

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We report measurements of energy-dependent attosecond photoionization delays between the two outer-most valence shells of N2O and H2O. The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N2O, whereas the delays in H2O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N2O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to ∼110 as. The unstructured continua of H2O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.Photoionization and photoelectron spectroscopies are powerful approaches to measuring the electronic structure of matter [1,2]. A complete quantum-mechanical description of photoionization, both in the time and frequency domains, requires the amplitude and phase of all dipole matrix elements, e.g. in a partial-wave expansion. Most experiments to date measure photoionization cross sections which are described by the sum of squared moduli of individual partial-wave dipole matrix elements. Cross sections thus contain no information about the partial-wave phase shifts. In contrast, photoelectron angular distributions are highly sensitive to partial-wave phase shifts [3,4] between continua associated with the same ionic state. Phase-shifts between continua associated with different ionization thresholds are not measurable in the frequency domain because the lack of spectral overlap between the corresponding photoelectrons erases the coherence required to measure such phase shifts.In this letter, we show that attosecond metrology can be employed to measure this information in molecular photoionization. Specifically, we study the effect of molecular shape resonances on the measured photoionization delays. When the combined molecular (or atomic) and centrifugal potential felt by the photoelectron displays a barrier, one or several quasi-bound states can emerge [5][6][7]. These resonances decay by tunneling through the potential barrier and often lead to a local enhancement of the photoionization cross section. Such shape resonances have so far only been measured by frequency-resolved measurements. Here, we show that attosecond metrology provides access to the time-domain manifestation of shape resonances. In the case of N 2 O, our measurements indeed reveal surprisingly large delays reaching up to 160 as in the range of 20 to 40 eV. In contrast, delays measured at the same photon energies in H 2 O all lie below 50 as in magnitude. These results are interpreted by developing a theory of molecular photoionization delays relying on accurate molecular scattering calculations. This analysis shows that the delays measured ...

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Section: (7)mentioning

confidence: 99%

Attosecond Delays in Molecular Photoionization

et al. 2016

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“…Several groups have since embarked in the implementation of the vacuum ultraviolet (VUV) version of such experiments 85–87 . The technique has been implemented to investigate the ultrafast IR-induced solvent heating, 83 intramolecular dynamics of solvated species, 88–91 and interfacial electron transfer, 92 while others are exploring extensions into the attosecond regime 93 …”

Section: Photoionization From Liquidsmentioning

confidence: 99%

Photoemission and photoionization time delays and rates

Gallmann

Jordan

Wörner

et al. 2017

Structural Dynamics

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Ionization and, in particular, ionization through the interaction with light play an important role in fundamental processes in physics, chemistry, and biology. In recent years, we have seen tremendous advances in our ability to measure the dynamics of photo-induced ionization in various systems in the gas, liquid, or solid phase. In this review, we will define the parameters used for quantifying these dynamics. We give a brief overview of some of the most important ionization processes and how to resolve the associated time delays and rates. With regard to time delays, we ask the question: how long does it take to remove an electron from an atom, molecule, or solid? With regard to rates, we ask the question: how many electrons are emitted in a given unit of time? We present state-of-the-art results on ionization and photoemission time delays and rates. Our review starts with the simplest physical systems: the attosecond dynamics of single-photon and tunnel ionization of atoms in the gas phase. We then extend the discussion to molecular gases and ionization of liquid targets. Finally, we present the measurements of ionization delays in femto- and attosecond photoemission from the solid–vacuum interface.

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“…The experimental setup consists of an actively stabilized attosecond beam line [16] and a magnetic-bottle photoelectron spectrometer [17]. High-harmonic generation in a gas cell filled with 10 mbar argon is driven by a 1.5 mJ, 30-fs laser pulse centered at 800 nm.…”

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Ionization Delays That Stand Out

Landsman

Kling

2016

Physics

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We report measurements of energy-dependent photoionization delays between the two outermost valence shells of N 2 O and H 2 O. The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N 2 O, whereas the delays in H 2 O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N 2 O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to ∼110 as. The unstructured continua of H 2 O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.Photoionization and photoelectron spectroscopies are powerful approaches to measuring the electronic structure of matter [1,2]. A complete quantum-mechanical description of photoionization, both in the time and frequency domains, requires the amplitude and phase of all dipole matrix elements, e.g., in a partial-wave expansion. Most experiments to date measure photoionization cross sections, which are described by the sum of squared moduli of individual partial-wave dipole matrix elements. Cross sections thus contain no information about the partial-wave phase shifts. In contrast, photoelectron angular distributions are highly sensitive to partial-wave phase shifts [3,4] between continua associated with the same ionic state. Phase shifts between continua associated with different ionization thresholds are not measurable in the frequency domain because the lack of spectral overlap between the corresponding photoelectrons erases the coherence required to measure such phase shifts.In this Letter, we show that attosecond metrology can be employed to measure this information in molecular photoionization. Specifically, we study the effect of molecular shape resonances on the measured photoionization delays. When the combined molecular (or atomic) and centrifugal potential felt by the photoelectron displays a barrier, one or several quasibound states can emerge [5][6][7]. These resonances decay by tunneling through the potential barrier and often lead to a local enhancement of the photoionization cross section. Such shape resonances have so far only been measured by frequency-resolved techniques. Here, we show that attosecond metrology provides access to the time-domain manifestation of shape resonances. In the case of N 2 O, our measurements indeed reveal surprisingly large delays reaching up to 160 as in the range of 20 to 40 eV. In contrast, delays measured at the same photon energies in H 2 O all lie below 50 as in magnitude. These results are interpreted by developing a theory of molecular photoionization delays relying on accurate molecular scattering calculations. This analysis shows that the delays measured in...

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Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

Cited by 49 publications

References 42 publications

Attosecond Delays in Molecular Photoionization

Attosecond Delays in Molecular Photoionization

Photoemission and photoionization time delays and rates

Ionization Delays That Stand Out

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