Can spirals produced by interfering electron vortices reflect the initial-state orbital symmetry of atomic and aligned diatomic molecular targets with identical ionization potentials? First introduced by Ngoko Djiokap and coauthors, the idea of generating spiral patterns in the photoelectron momentum distribution of photoionized atoms, by coherently interfering a pair of electron vortices created using time-delayed oppositely circularly polarized laser pulses, has led to an interdisciplinary field in physics. This phenomenon was confirmed experimentally by the Wollenhaupt group, and was also reported in the case of molecules. Nowadays, its connection to optical vortices, and its target or strong-field regime dependences are still hot topics. In this context, Wang and coauthors used a two-dimensional quantum mechanical approach to theoretically examine the target dependence in the multiphoton regime, with a focus on initial orbital symmetries. As the authors explain for one- and two-photon ionization processes of H₂, N₂, and their companion atom Ar (with the same ionization potentials), the number of spiral arms turns out to be an effective means to capture the differences or similarities in the shape of the initial-state orbitals. Strikingly, there is an exquisite sensitivity of the spirals to the internuclear separation and alignment angles of the molecules with respect to the laser field. With atoms as reference, interference of electron vortices could be a powerful tool for photoemission orbital tomography in molecules, which would enable monitoring their dissociation.

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