TIME-OF-FLIGHT MEASUREMENTS WITH A CMA FOR SIMULTANEOUS ENERGY AND MASS DETERMINATIONS OF DESORBED IONS

A commercial double-pass cylindrical mirror analyzer (CMA) has been used to perform 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. It is shown 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** plus , O** plus , F** plus and Cl** plus desorption from a W left brace 100 right brace surface.