Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 67, Number 7
Monday–Friday, May 30–June 3 2022; Orlando, Florida
Session U07: Chiral Matter and Chiral LightRecordings Available
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Chair: Loren Greenman, Kansas State Room: Salon 5/6 |
Thursday, June 2, 2022 2:00PM - 2:12PM |
U07.00001: Turning elliptically polarized light into a highly efficient chiro-optical tool Laura Rego, David Ayuso Distinguishing the two opposite versions of a chiral molecule (enantiomers) is important in organic chemistry, materials science or biomedicine. However, chiral discrimination is challenging and requires an interaction with another chiral object. Chiral light, such as circularly or elliptically polarized light, has long served as a convenient tool for detecting the chirality of matter, but the chiro-optical signal is extremely weak because it relies on the interplay with the magnetic-field component of the wave. |
Thursday, June 2, 2022 2:12PM - 2:24PM |
U07.00002: New opportunities for imaging chiral nuclear dynamics in chiral molecules on ultrafast time scales with synthetic chiral light David Ayuso Chiral molecules exist in pairs of left- and right-handed enantiomers. These “mirror twins” behave identically unless they interact with another chiral “object”. Distinguishing them is vital, but also hard [1]. Traditional optical methods rely on the helical structure that circularly polarized light draws in space. However, the pitch of this helix is too large, which leads to weak enantio-sensitivity (usually below 0.1%) and poses major challenges for imaging chiral dynamics, especially on ultrafast time scales. |
Thursday, June 2, 2022 2:24PM - 2:36PM |
U07.00003: Ultrafast chiral imaging with photoelectron vortices Andres F Ordonez Lasso, Xavier Barcons, Maciej Lewenstein, Andrew Maxwell Molecular chirality plays a decisive role in determining the outcome of molecular reactions, plays a fundamental role in biological systems, and has an immense importance for the chemical industry. The investigation of the interaction between intense short pulses of light and chiral matter has unveiled an array of highly enantio-sensitive phenomena, among which photoelectron techniques have received much attention. Simultaneously, there is an ongoing effort aimed at generating and characterizing electron vortices – electron waves with a helical phase front carrying orbital angular momentum. Electron vortices are expected to provide fundamentally new ways to image chiral matter but their study has been mostly limited to electron transmission microscopy and their potential for ultrafast imaging remains largely unexplored. Here we provide what is to our knowledge the first example of how to exploit photoelectron vortices for the purposes of ultrafast imaging of molecular chirality. Namely, we predict that an intense, linearly polarized, few-cycle, infrared pulse can project the chirality of the molecule onto the photoelectron vortex resulting from the strong-field ionization event. We support our prediction with accurate TDSE simulations in a model chiral system. |
Thursday, June 2, 2022 2:36PM - 2:48PM |
U07.00004: Optimal Enantioselective Orientation of Chiral Molecules Excited by Femtosecond Laser Pulses Long Xu, Ilia Tutunnikov, Yehiam Prior, Ilya Averbukh The separation and discrimination of chiral enantiomers play an important role in various chemical, physical, and biological processes. To achieve chiral discrimination, enantioselective orientation induced by a pair of delayed cross-polarized femtosecond laser pulses has been recently proposed. However, no experiments have been implemented so far, partly due to the concerns that the required high-intensity pulses would result in non-negligible molecular ionization. In this work, we present a comprehensive study of the dependence of the induced enantioselective orientation on laser parameters. The enantioselective orientation is nearly proportional to the laser pulse energy at nonzero finite temperature and the optimal time delay corresponds to the moment of the maximum alignment induced by the first laser pulse. On the other hand, at zero temperature, the enantioselective orientation shows a complicated dependence on the laser parameters, including the laser pulse energy and time delay. We show that by optimizing the parameters, a significant (~ 10%) degree of enantioselective orientation can be achieved both at zero and 5 Kelvin of the rotational temperature. This study identifies realistic laser parameters for inducing the strong enantioselective orientation, which will, hopefully, stimulate experimental demonstration of the effect. The strong enantioselective orientation may be useful for enantiomeric excess analysis, as well as for enantioselective separation using inhomogeneous fields. |
Thursday, June 2, 2022 2:48PM - 3:00PM |
U07.00005: Atomic photoionization by multiple temporal pairs of slits Jean Marcel Ngoko Djiokap The 2015 prediction of Archimedean spirals from photoionization of atoms by time-delayed circularly-polarized light [1], confirmed experimentally [2,3] for multiphoton ionization [4], has opened up a new interdisciplinary research field on searching for potential applications of this matter-wave phenomenon by exploring a variety of targets, processes and regimes. Here, we study interactions between multiple temporal pairs of slits in coherent control of photoionization of S-state atoms using a pulse train of N+1 pairs evenly delayed in time by $\tau$ in which the two pulses in a pair with a delay $\tau_0$ are counter-rotating circularly polarized. For interacting two double-slit experiments, while Ramsey interference between two identical Archimedean spirals yields pairs of principal spirals, interference of two spirals with opposite handedness does not lead to spirals, but instead to crocodile-eye-like patterns with nictares~[5]. For more than two interacting experiments, the resulting patterns turn out just to be those two reference patterns modulated by different kinds of N-dependent time-energy Fraunhofer functions exhibiting diffraction-grating-like patterns~[5]. These results indicate applications in electron grating spectrometers. |
Thursday, June 2, 2022 3:00PM - 3:12PM |
U07.00006: Photoelectron momentum distribution for H2+ in elliptically polarized laser pulses Yonas A Gebre, Andreas Becker We study photoelectron momentum distributions resulting from the interaction of the hydrogen molecular ion when interacting with an elliptically polarized laser pulse. Our results are based on numerical solutions of the full three dimensional Schrödinger equation. The features of the angular distributions as a function of the ellipticity of the pulse will be discussed and compared with analytical predictions from previous molecular models. Extensions of the calculations to other molecules within the single-active-electron approximation will be discussed |
Thursday, June 2, 2022 3:12PM - 3:24PM |
U07.00007: Ionization of co- and counter-rotating electrons in ultrashort circularly polarized laser pulses Spencer R Walker, Lucas Kolanz, Joel A Venzke, Andreas Becker
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Thursday, June 2, 2022 3:24PM - 3:36PM |
U07.00008: Trojan Wave Packets in the Circularly Polarized and the Magnetic Fields on the multi-layer Langmuir type $(1)$ Helium trajectories with the inter-layer twist Matt Kalinski Consistently with our recently discovered theorem stating that the number of distinct classically shape-invariantly rotating electron configurations in the external magnetic field and the nuclear ion field may be at least the product of all foldings of surfaces obtained by putting each of the multi-dimensional gradient component of the Zero Velocity Surface to zero we have discovered a several highly symmetric configurations originated from the Langmuir type $(1)$ ``Hoop Earrings" rotating Helium-like model trajectories [1] with further small symmetry distortion by the Circularly Polarized electromagnetic field without the loss of its nature. Those were the $2N$ or $2N+1$ electron Helium trajectories consisting of two or many layers of electrons moving in phase on circles with electron configurations placed at the vertexes of angles of identical by type but only scaled regular polygons parallel in space. Here we extend the case to the situation when the neighboring layer polygnons are phase-shifted by the half of their external angle. The classical stabilization of the trajectories by the combination of fields further leads to the existence of non-dispersing localized wave packets moving around the trajectories. [1] M. Kalinski, et al., Phys. Rev. Lett. {bf 95}, 103001, (2005). |
Thursday, June 2, 2022 3:36PM - 3:48PM |
U07.00009: Polarization rotation of light in a gas of molecular superrotors Uri Steinitz, Ilia Tutunnikov, Erez Gershnabel, Jean-Michel Hartmann, Alexander A Milner, Valery Milner, Ilya Averbukh We present a detailed theoretical and experimental study of the rotation of the plane of polarization of light traveling through a gas of fast-spinning molecules. This effect is related to the polarization drag phenomenon predicted by Fermi a century ago and is a mechanical analog of the Faraday effect. In our experiments, molecules were spun up by an optical centrifuge and brought to the super-rotor state that retains its rotation for a relatively long time. Polarizability properties of fast-rotating molecules were analyzed considering the rotational Doppler effect and Coriolis forces. We used molecular dynamics simulations to account for intermolecular collisions. We found, both experimentally and theoretically, that the time dependence of the polarization rotation angle is nontrivial and nonmonotonic. This time dependence reflects the transfer of angular momentum from the rotating molecules to the macroscopic gas flow, which may lead to the birth of gas vortices. Moreover, we show that the long-term behavior of the polarization rotation is sensitive to the details of the intermolecular potential. Thus, the polarization drag effect measurement appears as a novel diagnostic tool for the characterization of intermolecular interaction potentials and studies of collisional processes in gases. |
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