The process of photoionization of an atom or molecule in the perturbative regime is described by the dipole matrix element between the initial bound and final continuum states of the active electron. In usual treatments of the photoeffect, the final state is represented by a plane-wave scattering state in which the ejected photoelectron is characterized by a definite linear momentum. We consider the photoeffect in which the ejected photoelectron is described by a vortex scattering state and characterized by a definite projection of its angular momentum on a given vortex axis. Although the plane-wave and vortex transition matrix elements can be expressed in terms of each other, the corresponding cross sections cannot. We develop a theory of the molecular photoeffect with vortex photoelectrons, which includes the introduction and analysis of various vortex photoionization observables and their averaging over molecular orientations. The averaging is essential for treating photoionization of randomly oriented molecules in the gas phase. We show that the averaged vortex differential cross sections reveal new chiral asymmetries caused by the chirality of the vortex photoelectron, which generalize the phenomenon of photoelectron circular dichroism. The theory is illustrated by calculations for the glyceraldehyde molecule described within the molecular zero-range potential model. We also propose and validate by calculations a scheme based on a ring-shaped forked grating which allows, at least in principle, to verify our predictions experimentally.

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• Atomic & molecular processes in external fields
• Single- and few-photon ionization & excitation
• Molecules
• Dipole approximation
• Perturbative methods