Angular dependence of photoemission time delay in helium

Heuser, Sebastian; Galán, Álvaro Jiménez; Cirelli, Claudio; Marante, Carlos; Sabbar, Mazyar; Boge, Robert; Lucchini, Matteo; Gallmann, L.; Ivanov, Igor; Kheifets, Anatoli; Dahlström, Jan Marcus; Lindroth, Eva; Argenti, Luca; Martín, Fernando; Keller, U.

doi:10.1103/physreva.94.063409

Cited by 143 publications

(146 citation statements)

References 47 publications

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“…In particular, if the final channels do not have the same angular distribution, the time delay is expected to exhibit an angular dependence induced by the probe stage. In a recent joint theoretical and experimental work, Heuser et al [15] …”

Section: Photoionization Time Delaymentioning

confidence: 99%

Control of photoemission delay in resonant two-photon transitions

et al. 2017

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The photoelectron emission time delay τ associated with one-photon absorption, which coincides with half the Wigner delay τ W experienced by an electron scattered off the ionic potential, is a fundamental descriptor of the photoelectric effect. Although it is hard to access directly from experiment, it is possible to infer it from the time delay of two-photon transitions, τ (2) , measured with attosecond pump-probe schemes, provided that the contribution of the probe stage can be factored out. In the absence of resonances, τ can be expressed as the energy derivative of the one-photon ionization amplitude phase, τ = ∂ E arg D Eg , and, to a good approximation, τ = τ (2) − τ cc , where τ cc is associated with the dipole transition between Coulomb functions. Here we show that, in the presence of a resonance, the correspondence between τ and ∂ E arg D Eg is lost. Furthermore, while τ (2) can still be written as the energy derivative of the two-photon ionization amplitude phase,Eg , it does not have any scattering counterpart. Indeed, τ (2) can be much larger than the lifetime of an intermediate resonance in the two-photon process or more negative than the lower bound imposed on scattering delays by causality. Finally, we show that τ (2) is controlled by the frequency of the probe pulse, ω IR , so that by varying ω IR , it is possible to radically alter the photoelectron group delay.

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Section: Photoionization Time Delaymentioning

confidence: 99%

Control of photoemission delay in resonant two-photon transitions

et al. 2017

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“…More recently, this type of experiments have been used for spectral phase determination of photoelectrons from autoionizing states [6,7] and for the measurement of relative time delays in laser-assisted photoionization from different initial states in solids [8] and atoms [9][10][11]. Relative time delays have also been measured between different atomic species [12][13][14], between single and double ionization [15], between different angles of photoemission [16] and between the ion ground state and shake-up states [17]. In the case of atomic photoionization it has been established that the measured atomic delay τ A can be separated into a Wigner-like delay [18][19][20], τ W , here associated with the one-photon XUV ionization process, and a contribution from the interaction with the laser and long-range ionic field, τ CC , called the continuum-continuum delay (or Coulomb-laser coupling delay) [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Attosecond delays in laser-assisted photodetachment from closed-shell negative ions

Lindroth

Dahlström

2017

Phys. Rev. A

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We study laser-assisted photodetachment time delays by attosecond pulse trains from the closedshell negative ions F − and Cl − . We investigate the separability of the delay into two contributions: (i) the Wigner-like delay associated with one-photon ionization by the attosecond pulse train and (ii) the delay associated with exchange of an additional laser photon in the presence of the potential of the remaining target. Based on the asymptotic form of the wave packet, the latter term is expected to be negligible because the ion is neutralized leading to a vanishing laser-ion interaction with increasing electron-atom separation. While this asymptotic behavior is verified at high photoelectron energies, we also quantify sharp deviations at low photoelectron energies. Further, these low-energy delays are clearly different for the two studied anions indicating a breakdown of the universality of laser-ion induced delays. The fact that the short-range potential can induce a delay of as much as 50 as can have implications for the interpretation of delay measurements also in other systems that lack long-range potential.

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“…Given the s-symmetry of the ground state helium atom, one might expect that the photoemission delay is fully isotropic and does not exhibit an angular dependence. However, we could show that the two-photon nature of the RABBITT process yields a superposition of s- and d-like continuum wavefunctions, which results in a strong angular dependence of the measured delay 43 (see Fig. 3).…”

Section: Ionization Dynamics In Atomsmentioning

confidence: 92%

“…Electrons from these two dominant pathways are superimposed for a given final electron energy. Due to the different spatial symmetry, the mixing ratio of these two channels depends on the detection angle with respect to the polarization axis, which leads to the observed angular dependence of the photoemission time delay 43 . Particular care has therefore to be taken when interpreting angularly integrated photoemission delay data.…”

Section: Ionization Dynamics In Atomsmentioning

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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Angular dependence of photoemission time delay in helium

Cited by 143 publications

References 47 publications

Control of photoemission delay in resonant two-photon transitions

Control of photoemission delay in resonant two-photon transitions

Attosecond delays in laser-assisted photodetachment from closed-shell negative ions

Photoemission and photoionization time delays and rates

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