Professor Bierbaum's research focuses on the development of new techniques in physical and organic chemistry and their application to studies of gas phase ion chemistry. These studies probe the kinetics, dynamics and thermochemistry of a wide variety of gas phase ion-molecule reactions which have fundamental importance as well as relevance to atmospheric and interstellar chemistry. Two tandem flowing afterglow-selected ion flow tube instruments have been designed and constructed, one of which incorporates drift capabilities for the study of reactivity as a function of translational energy, as well as a new triple quadrupole detector for the structural and energetic characterization of gas phase ions. Current studies include nucleophilic substitution reactions (as a function of kinetic energy or microsolvation, deuterium kinetic isotope effects, competition with elimination processes), establishing the basicity and bond energies of many prototypical organic compounds (ethylene, benzene, propylene and toluene) and species of atmospheric interest (sulfur and peroxy compounds), employing isotopic labels to explore reaction mechanisms, and probing the chemistry of polycyclic aromatic hydrocarbon cations, which have been proposed as carriers of the Diffuse Interstellar Bands.