MASSES OF STABLE NEON ISOTOPES DETERMINED AT PARTS-PER-BILLION PRECISION BY FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETRY

Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry has been used to determine the masses of the stable neon isotopes, Ne-20 and Ne-22. From the mass difference, m(H-2(2) O-16+) - m(Ne-20+) = 0.030 677 480(67) u and previous accurate measurements of the Masses of O-16 and H-1, we have determined the atomic mass of Ne-20 as 19.992 440 691(90) u. From the measured mass difference, m(Ne-22+) - m(Ne-20+) = 1.998 943 585(290) u, the atomic mass of Ne-22 has been calculated as 21.991 384 276(304) u. Both of these newly determined isotopic masses are significantly more precise (factor of 24 for Ne-20 and factor of 6 for Ne-22), and deviate significantly (e.g. by more than 2sigma(accepted) for Ne-20) relative to the accepted values in the 1983 Atomic Mass Evaluation (based on nuclear reaction data), but are in excellent agreement with prior (less precise) magnetic sector-based mass-spectrometric measurements of these masses. The calculated two-neutron separation energy for Ne-22/Ne-20 is 17 126 662(270) eV.