Simultaneous SIMS, EID, and flash-filament investigations of the interaction of gases with a tungsten surface

A UHV system, containing a heatable (up to >2600 °K) W ribbon target, a Finkelstein ion source (Ar+, 2 keV) with magnetic mass separator, an electron source (300 eV), a quadrupole secondary ion mass filter with a counting channel electron multiplier and a quadrupole gas analyzer, is used for the study of the adsorption and desorption of H2, O2, and CO on W by simultaneous, i.e., fast interchanging "static" SIMS [secondary (ion induced) ion mass spectroscopy] and EID [electron induced (ion) desorption] and by flash-filament measurements. Different binding states can be distinguished. The emission cross sections of the adsorbate-specific ions by ion bombardment depend far less upon the gas exposure (and therefore upon the coverage) than those corresponding to electron bombardment.