Ion Balance Mass Spectrometry

We have developed a technique to simultaneously compare the cyclotron frequencies of two single ions to obtain atomic mass ratios with fractional accuracies at or below 10−11. Much like a balance scale, this two-ion technique cancels many sources of noise and error – chief among them magnetic field noise. The new mass comparisons are used in combination with γ-ray wavelength measurements, performed by the Institut Laue-Langevin/National Institute of Standards and Technology, to perform the most direct test of Einstein’s mass-energy relationship E = mc2. The increased precision and long measurement times also lead to the discovery of a new cyclotron frequency shift arising from polarization forces. This shift allowed the most accurate measurement of the dipole moment of a charged molecule (CO+), as well as a new method for non-destructively measuring the quantum state of a single molecule.