A multiparticle 3d imaging technique to study the structure of molecular ions

Abstract

When energetic molecular ions ( E ion = 0.1–0.5 MeV/amu) pass through thin solid targets a Coulomb explosion ensues due to the rapid (∼ 10 −17 s) stripping of the valence electrons. This process has been successfully used to derive stereochemical information on diatomic and on selected triatomic ions. In order to investigate more complex molecular ions as well as to obtain more accurate and detailed structure information, a large area, multiparticle, position and time-sensitive detector has been developed to detect all atomic fragments in coincidence. The requirement of multiparticle detection independent of the relative particle positions leads to a rather complex data-readout and -reduction system containing ~ 650 analog-to-digital conversions per event. The system relies heavily on techniques developed for high energy physics experiments during recent years. The single event resolution of the apparatus with respect to bond-lengths and -angles has been studied by Monte Carlo simulations and is typically a few percent.