Resonance ionization of neutral atoms with applications to surface science, noble gas detection and biomedical analysis

Abstract

AbstractResonance ionization of neutral atoms using narrow‐band tunable lasers to stepwise excite through one or more energy levels, and leading to photoionization, is becoming recognized as an emerging analytical technique having a number of unique properties. These include very high sensitivity, as saturated ionization in a well‐defined volume is possible for most elements, very high element selectivity in the ionization process, as energy levels are unique to each element, and generality, enabling ionization of all elements in the periodic table except He and Ne. In solid‐source mass spectrometry, resonance ionization spectroscopy is a post‐ionization technique, thereby achieving significant advantages by the separation of ionization from atomization.Combining resonance ionization with mass spectrometry has enabled measurements that heretofore were not feasible. The technique is being applied to a variety of new analytical problems and is showing significant promise. By combining ion sputtering with resonance ionization of the preponderant neutral population, more quantitative measurements are possible of semiconductor materials, especially at surfaces or interfaces. For biomedical applications, the high ionization efficiency, coupled with the high selectivity, allows accurate trace element determinations using microliter‐sized samples. Noble gas analyses have become possible from samples containing only a few thousand krypton atoms. Examples from each of the above application areas will be discussed.