Gas Phase            

In gas phase experiments we study electron capture reactions by molecules using negative ion mass spectrometry and time-of-flight techniques. The targets of interest concern molecules used as feed gases in material processing plasmas, molecules of atmospheric and interstellar interest and biologically relevant molecules, i.e. building blocks of proteins, DNA etc.

Experiments are extended to electron capture reactions by thermally excited molecules or molecules excited by IR or UV laser absorption.

Cluster            

In the cluster experiments we study relaxation phenomena, intracluster electron transfer processes and also ion-molecule reactions, e. g. nucleophilic displacement (SN₂) reactions following resonant electron capture to homogeneous and heterogeneous molecular aggregates formed via supersonic beam expansion.

In a heterogeneous cluster, e.g. a nucleophile can selectively be generated under controlled conditions from one component which then reacts with the second component within a binary cluster.

Surface            

In the surface UHV experiments electron and photon induced reactions in condensed and adsorbed molecules are studied with the emphasis on the formation and evolution of negative ion resonances. We find remarkable surface enhancements for dissociative capture reactions and are exploring the potential of low energy electron beams for controled surface modifications.

The experimental methods include electron stimulated desorption of ions, thermal desorption of neutrals, infrared-reflection-absorption spectroscopy (IRRAS) for monitoring reactions directly in the substrate and electron transmission through thin molecular films.

Laser-Induced Acoustic Desorption             

In order to study the molecular mechanisms of low-energy electron induced DNA strand breaks we developed a new technique to investigate electron interaction with larger and hence fragile biomolecules. We employ laser-induced acoustic desorption (LIAD) of biomolecules such as nucleosides, sugarphosphates and nucleotides. This is a useful method to transfer exclusively neutral and intact molecules into the gas phase. The desorbed molecules then interact with an electron beam to create negative ions. The energy dependence of the generated anions is analyzed by mass spectrometry.

The construction of the apparatus is still in progress, but we hope to elucidate soon the question, where an electron gets localised on DNA, and which bond cleavages finally lead to strand breaks.

Microarray            

Shortly, more information will be available...