The location of hydrogen isotopes is imaged in austenitic stainless steel and model materials using local-electrode atom-probe (LEAP) tomography and trapping energies are measured by thermal desorption spectroscopy. LEAP tomography has sub-nanometer resolution and excellent compositional sensitivity due to pulse counting techniques. Site-specific sample preparation is possible using focused-ion beam, enabling us to show trapping at low density features, such as 4 grain boundaries in a model materials (commercially pure nickel and ultra-fine-grain Al-Mg). LEAP tomography is the only known technique to measure trapping to solute atoms (here, nitrogen in 21Cr-6Ni-9Mn austenitic stainless steel), and this report is the first use of the technique to image trapping in austenitic stainless steels. The experimental work is compared with first-principles calculations of the binding energy of hydrogen isotopes to solid solution nitrogen in stainless steels. 5 ACKNOWLEDGMENTS

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