Neutron skin thickness ($\mathrm{\Delta }{r}_{\mathrm{np}}$) of nuclei and the inferred nuclear symmetry energy are of critical importance to nuclear physics and astrophysics. It is traditionally measured by nuclear processes with significant theoretical uncertainties. We recently proposed an indirect measurement of the $\mathrm{\Delta }{r}_{\mathrm{np}}$ by charged hadron multiplicities in central isobaric collisions at relativistic energies, which are sensitive to nuclear densities. In this Letter, we propose a direct measurement of the $\mathrm{\Delta }{r}_{\mathrm{np}}$ by using net-charge multiplicities in ultraperipheral (grazing) collisions of those isobars, under the assumption that they are simple superimposition of nucleon-nucleon interactions. We illustrate this novel approach by the trento and urqmd models.

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• Charge distributions
• Nucleon distribution
• Nucleon-nucleon interactions
• Relativistic heavy-ion collisions
• Symmetry energy