Precision mass ratios of mass-3 ions

Precision atomic masses of hydrogen, deuterium and helium-3 are important fundamental constants with application to a wide range of physical science. Using a rebuilt and improved Penning trap mass spectrometer, we are measuring the ion mass ratios HD$^{\mathrm{+}}$/H$_{\mathrm{3}}^{\mathrm{+}}$, $^{\mathrm{3}}$He$^{\mathrm{+}}$/H$_{\mathrm{3}}^{\mathrm{+}}$ and $^{\mathrm{3}}$He$^{\mathrm{+}}$/HD$^{\mathrm{+}}$. The results will help resolve the current four-sigma discrepancy for the mass of $^{\mathrm{3}}$He.