Strong-field control and enhancement of chiral response in bi-elliptical high-order harmonic generation: an analytical model

Ayuso, David Fernández; Decleva, Piero; Patchkovskii, Serguei; Smirnova, Olga

doi:10.1088/1361-6455/aabc95

Cited by 30 publications

(37 citation statements)

References 73 publications

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“…Our present results show that a good agreement between experiment and theory can also be achieved for much more complex systems, i.e., chiral molecules. This agreement is an important conclusion of our work that validates the theoretically predicted origin [26,37,38] of the circular dichroism in bicircular driving fields.…”

Section: A Mechanisms Of Chiral Discriminationsupporting

confidence: 90%

“…Our theoretical analysis shows that the measured CD is entirely dominated by laser-field-induced magnetic-dipole transitions in the molecular cation between ionization and recombination. In this way, our findings lend support to the predictions and conclusions of previous theoretical work [26,37,38]. The observed chiral discrimination thus relies on subfemtosecond electron dynamics driven by the magnetic-field component of the laser field, offering the opportunity to study a new class of laser-controlled charge migration [30].…”

Section: Introductionsupporting

confidence: 88%

“…The application of BHHG to study static and time-dependent symmetries of atoms and molecules has been termed bicircular high-harmonic spectroscopy (BHHS) [34][35][36]. Its potential for the study of chiral molecules has ignited some theoretical interest [26,37,38], whereby inconsistent predictions regarding the expected degree of circular dichroism have been made (∼3% in Ref. [37] versus up to 80% in the previous study [26]).…”

Section: Introductionmentioning

confidence: 99%

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Chiral Discrimination through Bielliptical High-Harmonic Spectroscopy

Baykusheva

Wörner

2018

Phys. Rev. X

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Molecular chirality plays an essential role in most biochemical processes. The observation and quantification of chirality-sensitive signals, however, remains extremely challenging, especially on ultrafast timescales and in dilute media. Here, we describe the experimental realization of an all-optical and ultrafast scheme for detecting chiral dynamics in molecules. This technique is based on high-harmonic generation by a combination of two-color counterrotating femtosecond laser pulses with polarization states tunable from linear to circular. We demonstrate two different implementations of chiral-sensitive high-harmonic spectroscopy on an ensemble of randomly oriented methyloxirane molecules in the gas phase. Using two elliptically polarized fields, we observe that the ellipticities maximizing the harmonic signal reach up to 4.4 AE 0.2% (at 17.6 eV). Using two circularly polarized fields, we observe circular dichroisms ranging up to 13 AE 6% (28.3-33.1 eV). Our theoretical analysis confirms that the observed chiral response originates from subfemtosecond electron dynamics driven by the magnetic component of the driving laser field. This assignment is supported by the experimental observation of a strong intensity dependence of the chiral effects and its agreement with theory. We moreover report and explain a pronounced variation of the signal strength and dichroism with the driving-field ellipticities and harmonic orders. Finally, we demonstrate the sensitivity of the experimental observables to the shape of the electron hole. This technique for chiral discrimination will yield femtosecond temporal resolution when integrated in a pump-probe scheme and subfemtosecond resolution on chiral charge migration in a self-probing scheme.

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Section: A Mechanisms Of Chiral Discriminationsupporting

confidence: 90%

Section: Introductionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Chiral Discrimination through Bielliptical High-Harmonic Spectroscopy

Baykusheva

Wörner

2018

Phys. Rev. X

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“…Our next step is to identify the molecule-specific enantio-sensitive structure in Eqs. (7) and (8). That is, we will be looking for molecule-specific pseudoscalars; quantities that change sign upon parity inversion.…”

Section: A Photoelectron Circular Dichroismmentioning

confidence: 99%

Generalized perspective on chiral measurements without magnetic interactions

2018

Self Cite

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We present a unified description of several methods of chiral discrimination based exclusively on electric-dipole interactions. It includes photoelectron circular dichroism (PECD), enantio-sensitive microwave spectroscopy (EMWS), photoexcitation circular dichroism (PXCD) and photoelectron-photoexcitation circular dichroism (PXECD). We show that, in spite of the fact that the physics underlying the appearance of a chiral response is very different in all these methods, the enantio-sensitive and dichroic observable in all cases has a unique form. It is a polar vector given by the product of (i) a molecular pseudoscalar and (ii) a field pseudovector specified by the configuration of the electric fields interacting with the isotropic ensemble of chiral molecules. The molecular pseudoscalar is a rotationally invariant property, which is composed from different molecule-specific vectors and in the simplest case is a triple product of such vectors. The key property that enables the chiral response is the non-coplanarity of the vectors forming such triple product. The key property that enables chiral detection without relying on the chirality of the electromagnetic fields is the vectorial nature of the enantio-sensitive observable. Our compact and general expression for this observable shows what ultimately determines the efficiency of the chiral signal and if, or when, it can reach 100%. We also discuss the differences between the two phenomena, which rely on the bound states, PXCD and EMWS, and the two phenomena using the continuum states, PECD and PXECD. Finally, we extend these methods to arbitrary polarizations of the electric fields used to induce and probe the chiral response.

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“…[42,[55][56][57][58][59][60]). Applications include analysis of enantio-sentitivity of HHG in chiral molecules [61][62][63], description of HHG by atoms with initial p orbitals [64,65], and control of the spin polarization of recolliding electrons [66].…”

Section: Introductionmentioning

confidence: 99%

Analytic description of high-order harmonic generation in the adiabatic limit with application to an initial s state in an intense bicircular laser pulse

et al. 2019

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An analytic description of high-order harmonic generation (HHG) is proposed in the adiabatic (low-frequency) limit for an initial s state and a laser field having an arbitrary wave form. The approach is based on the two-state time-dependent effective range theory and is extended to the case of neutral atoms and positively charged ions by introducing ad hoc the Coulomb corrections for HHG. The resulting closed analytical form for the HHG amplitude is discussed in terms of real classical trajectories. The accuracy of the results of our analytic model is demonstrated by comparison with numerical solutions of the time-dependent Schrödinger equation for a strong bicircular field composed of two equally intense components with carrier frequencies ω and 2ω and opposite helicities. In particular, we demonstrate the effect of ionization gating on HHG in a bicircular field, both for the case that the two field components are quasimonochromatic and for the case that the field components are time-delayed short pulses. We show how ionization in a strong laser field not only smooths the usual peak structures in HHG spectra but also changes the positions and polarization properties of the generated harmonics, seemingly violating the standard dipole selection rules. These effects appear for both short and long incident laser pulses. In the case of time-delayed short laser pulses, ionization gating provides an effective tool for control of both the HHG yield and the harmonic polarizations [Frolov et al., Phys. Rev. Lett. 120, 263203 (2018)]. For the case of short laser pulses, we introduce a simple two-dipole model that captures the physics underlying the harmonic emission process, describing both the oscillation patterns in HHG spectra and also the dependence of the harmonic polarizations on the harmonic energy.

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Strong-field control and enhancement of chiral response in bi-elliptical high-order harmonic generation: an analytical model

Cited by 30 publications

References 73 publications

Chiral Discrimination through Bielliptical High-Harmonic Spectroscopy

Chiral Discrimination through Bielliptical High-Harmonic Spectroscopy

Generalized perspective on chiral measurements without magnetic interactions

Analytic description of high-order harmonic generation in the adiabatic limit with application to an initial s state in an intense bicircular laser pulse

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