Vortex beams are exotic states of classical light fields that contain orbital angular momentum (OAM) due to their space-dependent phases. While the experimental realization of intense low-frequency optical vortices has led to the discovery and application of OAM conservation in high-harmonic generation, there is not a comparable signature of light's OAM on photoelectrons. Here we propose using a linear combination of vortex modes, referred to as a vector vortex beam, for strong-field ionization of atoms. We then demonstrate that the input vortex beam's position-dependent phase can be obtained from the resulting electron momentum distribution following strong-field ionization. We validate this method by performing classical trajectory Monte Carlo simulations and comparing momentum distributions corresponding to different ionization locations within the beam profile, demonstrating that one can unambiguously determine the ionizing radiation's OAM index. These results are suitable for the added control offered by vortex light compared to Gaussian or plane-wave radiation in intense light-matter interactions.

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• Angular momentum of light
• Electronic excitation & ionization
• Multiphoton or tunneling ionization & excitation
• Optical vortices
• Strong field ionization & excitation
• Structured light