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This theoretical study identifies three fundamental geometric mechanisms that explain spin-dependent and chirality-sensitive effects when chiral molecules are ionized by circularly polarized light. The researchers demonstrate that these mechanisms, arising solely from electric dipole interactions, can be described by three pseudovectors representing geometric properties in spin space and real space, simplifying the ten independent parameters previously thought necessary to describe this process. The framework is generalizable to other light-matter interactions including photoexcitation and multiphoton processes.
Why it matters
This work provides a unified geometric understanding of chirality-induced spin selectivity in photoionization, which could inform the design of more efficient methods for distinguishing between mirror-image molecules (enantiomers) in chemistry and pharmaceuticals. The simplified theoretical framework may accelerate development of optical techniques for chiral molecule detection and separation.
arXiv:2603.02735v3 Announce Type: replace
Abstract: We examine spin-resolved photoionization of randomly oriented chiral molecules via circularly polarized light, and revisit earlier predictions of Cherepkov (J. Phys. B: Atom. Mol. Phys. 16, 1543, 1983). We will show that the dynamical origin of spin- and enantio-sensitive observables arise from two intrinsic mechanisms that are quantified by two pseudovectors stemming from the geometric properties of the photoionization dipoles in spin space and in real space, and an extrinsic mechanism which is a directional bias introduced by the well-defined direction of light polarization. These mechanisms arise solely from electric dipole interactions. Consequently, this means that the ten independent parameters that was earlier predicted by Cherepkov to fully describe spin-resolved photoionization of chiral molecules can be reduced as moments of these three pseudovectors. We also find that the molecular pseudoscalars describing the spin- and enantio-sensitive components of the yield can be described by the flux of these pseudovectors through the energy shell, which changes sign upon switching enantiomers. Our results provide compact expressions for these observables which provide an intuitive picture on what determines the strength of these spin- and enantio-sensitive observables. The approach can be readily generalized to photoexcitation, multiphoton processes, and arbitrary field polarizations. Regardless of the specific driving conditions, the resulting spin- and enantio-sensitive observables are still controlled by the same three pseudovectors, underscoring their universal role as the primary generators of chirality-induced spin asymmetries, emphasizing their fundamental geometric origin and the universality of the mechanism identified here.