ACCURATE ATOMIC MASSES FOR FUNDAMENTAL METROLOGY

We have measured the atomic masses of ten species with a typical accur acy of 10(-10) by comparing the cyclotron frequencies of 20 different pairs of alternately trapped ions. The mass of Si-28 provides a possib le route to realizing an atomic standard of mass. The neutron separati on energies for N-15 and C-13 determined from these mass measurements suggest the need to recalibrate gamma-ray energies in the 2 to 13 MeV range, and may lead to an independent determination of both the fine s tructure constant alpha and the molar Planck constant N(A)h with a pre cision approaching 10(-7).