Time-of-flight measurements with a CMA for simultaneous energy and mass determinations of desorbed ions

Abstract

Using a commercial double-pass cylindrical mirror analyzer (CMA) we have made mass, energy, and angle-resolved measurements of positively charged ions emitted from a surface by electron-stimulated desorption. Because the dispersive character of the CMA selects the ion energy, the mass can be uniquely and simultaneously determined from the flight time in the analyzer. We show that this can be achieved with relatively simple additional electronics, and unity mass resolution is possible up to at least mass 20. Some of the principles, limitations, and capabilities of the technique are described and illustrated by measurements of H+, O+, F+ and Cl+ desorption from a W{100} surface.