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Generalized perspective on chiral measurements without magnetic interactions
摘要： We present a unified description of several methods of chiral discrimination based exclusively on electric-dipole interactions. It includes photoelectron circular dichroism (PECD), enantiosensitive 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 enantiosensitive 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 noncoplanarity 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 enantiosensitive 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.
关键词： photoelectron-photoexcitation circular dichroism,electric-dipole interactions,field pseudovector,enantiosensitive microwave spectroscopy,photoexcitation circular dichroism,molecular pseudoscalar,chiral discrimination,photoelectron circular dichroism
更新于2025-09-23 15:23:52
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Asymmetric photoelectron emission from chiral molecules using a high repetition rate laser
摘要： In the chiro-optical phenomenon known as photoelectron circular dichroism, the angular distribution of electrons ionized from chiral molecules by circularly polarized light pulses has been found to be anti-symmetric with respect to the direction of the light propagation. To study this phenomenon, chiral molecules were multiphoton ionized with a femtosecond laser in our laboratory. Using a simple stereo-detection setup, direct measurements of the asymmetry for the exemplar aromatic chiral molecule 1-phenylethanol were made using 260 nm pulses produced at a rate of 1 MHz. It was found that the asymmetry had a linear dependence on Stokes’ S3 parameter indicating that the photoelectron circular dichroism is due to a single photon process from the excited state of the molecule. This is in contrast to previous and new results for camphor where a more complex dependence on S3 suggested that selective excitation of molecules with certain orientations was influential.
关键词： photoelectron circular dichroism,circularly polarized light,asymmetry,Stokes’ S3 parameter,chiral molecules
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Photoelectron Circular Dichroism at the Few-Cycle Limit in the Tunnel Ionization Regime
摘要： Photoelectron circular dichroism (PECD) is a process that leads to a forward-backward asymmetry (with respect to the laser propagation direction) in photoelectron distributions created upon interaction of a circularly or elliptically polarized laser with a chiral molecule. The PECD effect has been shown in a broad range of ionization mechanisms from direct photoionization through multi-photon regime, above-threshold ionization to the tunnel ionization [1]. The fact that the effects of chirality can be observed in the tunnel ionization regime opens up the possibility to connect this fundamental effect to strong-field science with prospects for studying and driving sub-laser-cycle and attosecond phenomena connected to PECD [2]. However, a thorough understanding of PECD in the tunneling regime is of yet missing. In this study the effect of trajectory related parameters like electron energy or CEP on the PECD is investigated in order to determine the role of the scattering on the chiral potential.
关键词： few-cycle laser pulses,tunnel ionization,Photoelectron circular dichroism,chiral molecules
更新于2025-09-12 10:27:22
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Universality of photoelectron circular dichroism in the photoionization of chiral molecules
摘要： Photoionization of chiral molecules by circularly polarized radiation gives rise to a strong forward/backward asymmetry in the photoelectron angular distribution, referred to as photoelectron circular dichroism (PECD). Here we show that PECD is a universal effect that reveals the inherent chirality of the target in all ionization regimes: single photon, multiphoton, above-threshold and tunnel ionization. These different regimes provide complementary spectroscopic information at electronic and vibrational levels. The universality of the PECD can be understood in terms of a classical picture of the ionizing process, in which electron scattering on the chiral potential under the influence of a circularly polarized electric field results in a strong forward/backward asymmetry.
关键词： strong fields,photoelectron circular dichroism,chirality,multiphoton ionization
更新于2025-09-09 09:28:46