ACCURATE MASS SPECTROMETRY OF TRAPPED IONS

Abstract

The Penning trap Ion Cyclotron Resonance (ICR) method we use to weigh atomic masses is reviewed, and our plans for future measurements, new methods, and apparatus improvements are discussed. Our ultimate goal is to develop a new technique for measuring atomic masses with an accuracy of a few parts in 1012. We will do this by comparing the cyclotron frequencies of two simultaneously trapped ions. In order to successfully implement this new method we are developing a quieter, more sensitive DC SQUID-based detector and a new more harmonic trap, and we plan to use our classical squeezing techniques to reduce the effects of thermal noise. With our improved apparatus we will weigh Cs and Rb to help determine the fine structure constant α, weigh 29Si and 30Si as part of the current effort to replace the artifact kilogram standard with a Si crystal containing a known number of atoms, and measure the 3H-3He mass difference to help set a limit on the mass of the electron neutrino. Our higher accuracy will also enable us to ``weigh'' the neutron capture gamma rays of 28Si, 32S, and 48Ti to help determine the molar Planck constant NAh and the fine structure constant α. Finally, with a mass measurement accuracy \sim 10-12 we will be able to ``weigh'' chemical bonds.