Attosecond-resolved photoionization of chiral molecules

Beaulieu, Samuel; Comby, Antoine; Clergerie, Alex; Caillat, Jérémie; Descamps, D.; Dudovich, Nirit; Fabre, B.; Géneaux, Romain; Légaré, François; Petit, S.; Pons, B.; Porat, Gil; Ruchon, Thierry; Taïeb, Richard; Blanchet, Valérie; Mairesse, Y.

doi:10.1126/science.aao5624

Cited by 188 publications

(136 citation statements)

References 59 publications

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“…Calculation by Barth and Smirnova [6] predict an increase of the electron energy-integrated spin polarization with rising γ. Using equations (14)- (16) in [6] one can expect a relative increase of 43% between the experiment reported in [2] at γ = 1.24 and the present work at γ = 3.73. The strong but not completely known energy dependence of the detection solid angle of our spectrometer does not allow us to obtain a reliable energyintegrated spin polarization, thus a test of this prediction remains a goal for future experimental work.…”

Section: Counts Energysupporting

confidence: 55%

Spin and Angular Momentum in Strong-Field Ionization

et al. 2018

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The spin polarization of electrons from multiphoton ionization of Xe by 395 nm circularly polarized laser pulses at 6 · 10 13 W/cm 2 has been measured. At this photon energy of 3.14 eV the above threshold ionization peaks connected to Xe + ions in the ground state (J = 3/2, ionization potential Ip = 12.1 eV) and the first exicted state (J = 1/2, Ip = 13.4 eV) are clearly separated in the electron energy distribution. These two combs of ATI peaks show opposite spin polarizations. The magnitude of the spin polarization is a factor of two higher for the J = 1/2 than for the J = 3/2 final ionic state. In turn the data show that the ionization probability is strongly dependent on the sign of the magnetic quantum number.Light-driven ionization processes are sensitive to the spin of the electron. Surprisingly, this important and fundamental fact of light matter interaction is experimentally well validated only for the special cases of single photon and resonant enhanced two and three photon processes [1]. For strong-field ionization it rests on only one single experiment [2], which did not even resolve the quantum state from which the electron was ejected.The role of the spin in single photon ionization was adressed soon after the discovery of the electron spin [3]. Starting in the 1960s, it became clear that spin selectivity of single photon ionization of atoms and molecules is very general. Today it is well studied experimentally and theoretically (see [4] for a review). The generalization to the multiphoton regime was achieved first in pioneering theoretical work by Lambropoulus [5]. Recently Barth and Smirnova [6] predicted a high degree of spin polarization for strong-field ionization by circularly polarized femtosecond pulses. The proposed mechanism giving rise to spin sensitivity of strong-field ionization consists of two independent steps. The primary effect is that the nonadiabatic tunneling probability through a rotating barrier depends on the sign of the magnetic quantum number m l of the orbital. This finding was confirmed experimentally [7] and by solving the time-dependent Schrödinger equation [8] without invoking the concept of tunneling explicitly. Together with the strong binding energy dependence of strong-field ionization the m l dependence then leads to a spin selectivity. Because, due to the spinorbit interaction, the binding energy differs for parallel or antiparallel orientation of the spin with respect to the projection of the orbital angular momentum m l on the quantization axis.The purpose of the present paper is to experimentally show this theoretically suggested connection of spin, magnetic quantum number and binding energy in strongfield ionization. This relies on experimentally determining both: the ionization potential and the spin polarization of the electron. For xenon this is possible as illus-Schematics of multiphoton ionization in xenon by 395 nm (hν = 3.14 eV) laser pulses. The ground state ( 2 P , J = 3/2) and first excited state ( 2 P , J = 1/2) of Xe + differ by ∆Ip = 1.3 eV in i...

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Section: Counts Energysupporting

confidence: 55%

Spin and Angular Momentum in Strong-Field Ionization

et al. 2018

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“…It is thus sensitive to attosecond ionic dynamics. Phase-resolved PECD [41] probes the difference between the photoionization delays of electrons ejected forward and backward with respect to the laser propagation axis, revealing the influence of the chiral molecular potential on the scattering dynamics of the outgoing electrons. ESCARGOT probes influence of the optical chirality on these scattering dynamics, and is thus complementary to phase-resolved PECD.…”

Section: Discussionmentioning

confidence: 99%

Controlling Subcycle Optical Chirality in the Photoionization of Chiral Molecules

et al. 2019

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Controlling the polarization state of electromagnetic radiation enables the investigation of fundamental symmetry properties of matter through chiroptical processes. Over the past decades, many strategies have been developed to reveal structural or dynamical information about chiral molecules with high sensitivity, from the microwave to the extreme ultraviolet range. Most schemes employ circularly or elliptically polarized radiation, and more sophisticated configurations involve, for instance, light pulses with time-varying polarization states. All these schemes share a common propertythe polarization state of light is always considered as constant over one optical cycle. In this study, we zoom into the optical cycle in order to resolve and control a subcyle attosecond chiroptical process. We engineer an electric field whose instantaneous chirality can be controlled within the optical cycle, by combining two phase-locked orthogonally polarized fundamental and second harmonic fields. While the composite field has zero net ellipticity, it shows an instantaneous optical chirality which can be controlled via the two-color delay. We theoretically and experimentally investigate the photoionization of chiral molecules with this controlled chiral field. We find that electrons are preferentially ejected forward or backward relative to the laser propagation direction depending on the molecular handedness, similarly to the well-established photoelectron circular dichroism process. However, since the instantaneous chirality switches sign from one half cycle to the next, electrons ionized from two consecutive half cycles of the laser show opposite forward/backward asymmetries. This chiral signal, termed here as ESCARGOT (Enantiosensitive Sub-Cycle Antisymmetric Response Gated by electric-field rOTation), provides a unique insight into the influence of instantaneous chirality in the dynamical photoionization process. More generally, our results demonstrate the important role of sub-cycle polarization shaping of electric fields, as a new route to study and manipulate chiroptical processes.

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“…Based on a semiclassical model, the time delay of a temporary retrapping of a photoelectron by the atomic potential is revealed for the near threshold photoelectron [23]. Extending the photoelectron interferometry in strong-field ATI regime to chiral molecules, an attosecond time delay was revealed between electrons ejected forward and backward relative to the laser propagation direction [24].…”

Section: Introductionmentioning

confidence: 99%

Semiclassical analysis of photoelectron interference in a synthesized two-color laser pulse

Feng

Luo

et al. 2019

Phys. Rev. A

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We measure the photoelectron energy spectra from strong-field ionization of Kr in a two-color laser pulse consisting of a strong 400-nm field and a weak 800-nm field. The intensities of the main above-threshold ionization (ATI) and sideband peaks in the photoelectron energy spectra oscillate roughly oppositely with respect to the relative phase between the two-color components. We study the photoelectron interferometry in strong-field ATI regime from the view of interference of different electron trajectories in order to extend RABBITT type analysis to the strong-field regime. Based on the strong-field approximation model, we obtain analytical expressions for the oscillations of both ATI and sideband peaks with the relative phase. A phase shift of π/4 with respect to the field maximum of the two-color laser pulse is revealed for the interference maximum in the main ATI peak without including the effect of the atomic potential.

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Attosecond-resolved photoionization of chiral molecules

Cited by 188 publications

References 59 publications

Spin and Angular Momentum in Strong-Field Ionization

Spin and Angular Momentum in Strong-Field Ionization

Controlling Subcycle Optical Chirality in the Photoionization of Chiral Molecules

Semiclassical analysis of photoelectron interference in a synthesized two-color laser pulse

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