arXiv subjects

Andrés Ordóñez

Publications and source records attributed to Andrés Ordóñez.

6 recordsLinked to original sources

arXiv2026

Chiral moments make chiral measures

We develop a family of chiral measures to quantify the chirality of a distribution and assign it a handedness. Our measures are built using the tensorial moments of the distribution, which naturally encode its spatial character, not only via its angular shape consistently with existing multipolar-moment approaches, but also its radial dependence. We combine these tensorial moments into a rotationally-invariant pseudoscalar using a newly-defined cross product and triple product for arbitrary symmetric tensors. We analyze these measures for a variety of toy-model distributions, providing intuition for the geometry and guiding the choice of chiral measure optimal for a given distribution. We also apply our measures to a physically-motivated example coming from photoionization in polychromatic chiral light. Our work provides a robust, flexible, intuitive, highly geometrical, and physically-driven framework for understanding and quantifying the chirality of a wide variety of distributions, together with an open-source software package that makes this toolbox readily applicable for the analysis of numerical or experimental data.

physics.data-an↗

arXiv2025

Theory of Non-Dichroic Enantio-Sensitive Chiroptical Spectroscopy

We show that the photoelectron angular distributions produced by elliptical and cross-polarized two-color laser fields interacting with randomly oriented chiral molecules decompose into four irreducible representations of the $D_{2h}$ point group. One of these ($A_u$) corresponds to a non-dichroic enantiosensitive (NoDES) contribution. This NoDES contribution has opposite sign for opposite enantiomers but remains invariant under reversal of the field ellipticity, enabling chirality detection that is robust against variations of the relative phase between orthogonal field components. We propose a protocol to isolate this component using only two velocity-map imaging projections and validate it through numerical simulations. Our calculations, performed in the two-photon resonantly-enhanced ionization, multi-photon, and strong-field ionization regimes with cross-polarized two-color fields show that the NoDES signal reaches about 1\% of the energy-resolved ionization yield, comparable to photoelectron circular dichroism and much larger than standard magnetic-dipole chiroptical effects. NoDES spectroscopy thus provides a symmetry-protected and phase-robust route to probe molecular chirality on the ultrafast time scale. The experimental confirmation of our theory is presented in the companion paper [L. Fede et al., arXiv:2512.19062 (2025)].

physics.chem-ph↗

arXiv2025

Non-Dichroic Enantio-Sensitive Chiroptical Spectroscopy

Chiroptical effects using circularly polarized light produce signals that change sign when switching either molecular handedness (enantiosensitivity) or the light helicity (circular dichroism). Here, we break this enantiosensitive-and-dichroic paradigm by measuring a new type of chiroptical signal which is enantiosensitive but not dichroic. We photoionize chiral molecules using a strong laser field and detect the three-dimensional photoelectron momentum distribution. The non-dichroic, enantiosensitive asymmetry is encoded in octupolar and higher multipolar terms in the photoelectron angular distribution, which appear in multiphoton ionization with elliptically polarized fields or cross polarized two-color fields. The robustness of the enantiosensitivity with respect to the relative phase between the vectorial components of the ionizing field represents an example of symmetry protection, and opens unexplored opportunities for imaging ultrafast dynamics in chiral molecules, such as enantiosensitive photoelectron spectroscopy with bright squeezed vacuum states.

physics.chem-ph↗

arXiv2025

All-optical coherent control of chiral electronic transitions for highly enantioselective photochemistry

Enantioselective photochemistry provides access to unique molecular structures and functions, with deep implications for fundamental science and industrial applications. Current methods for highly enantioselective photochemistry critically rely on chiral sensitisers, as circularly polarised light on its own yields vanishingly weak enantioselectivity. Here, we introduce a quantum control strategy to drive highly enantioselective electronic excitations in randomly oriented samples using a pulsed ($\sim$22 fs) IR laser and two of its harmonics, in the absence of intermediate resonances. Our approach addresses electronic transitions, does not require chiral sensitisers, or cold molecules, or long electronic coherence times, is relevant for liquid-phase samples, and remains effective over interaction regions extending across many laser wavelengths, even in the presence of dispersion. We show how, by 3D shaping the field's polarisation over the interaction region, we can achieve enantioselective coherent control over electronic population transfer. Our ab-initio simulations in the chiral molecule carvone yield a selectivity of $\sim$30 % in the populations of the first excited electronic state, three orders-of-magnitude higher than what is possible with circularly polarised light ($\sim$0.01 %). These results bring all-optical enantioselective photochemistry into the realm of practical applications.

physics.chem-ph↗

arXiv2024

Ultrafast TACOS -- Terahertz-Assisted Chiro-Optical Spectroscopy

We bring together the advantages of terahertz (THz) and optical spectroscopies to introduce TACOS (Terahertz-Assisted Chiro-Optical Spectroscopy), a novel approach for ultrafast and highly efficient imaging of molecular chirality and control over chiral electronic dynamics. We show how, using a THz pulse, we can induce a transient electronic orientation in a medium of randomly oriented chiral molecules that breaks the isotropy of the molecular sample. This symmetry breaking twists the nonlinear response of the medium to an ultrashort linearly polarised optical pulse in a highly enantiosensitive manner. As a result, the medium emits elliptically polarised light at new optical frequencies that records the molecular handedness via purely electric-dipole interactions. The long wavelength and period of the THz pulse enable both spatial coherence across the sample and a substantial degree of electronic orientation over the duration of the ultrashort optical pulse. TACOS does not require optical carrier-envelope phase stability or working in vacuum, and it creates exciting avenues for ultrafast and highly efficient chiral sensing and manipulation.

physics.optics↗

arXiv2023

Strong-field chiral imaging with twisted photoelectrons

Ultrafast imaging of molecular chirality is a key step towards the dream of imaging and interpreting electronic dynamics in complex and biologically relevant molecules. Here, we propose a new ultrafast chiral phenomenon exploiting recent advances in electron optics allowing access to the orbital angular momentum of free electrons. We show that strong-field ionization of a chiral target with a few-cycle linearly polarized 800 nm laser pulse yields photoelectron vortices, whose chirality reveals that of the target, and we discuss the mechanism underlying this phenomenon. Our work opens new perspectives in recollision-based chiral imaging.

physics.atom-ph↗