Trapped Ion Dynamics Group

Current research projects in the Trapped Ion Dynamics Group are designed to study the structural dynamics of nanoscale gas-phase species including small metal clusters and biomolecules. Please see our Group Page for a list of past and present researchers who have contributed to these projects.

Diffraction Measurements of Metal Cluster Symmetry

The study of small metal clusters has made extensive contributions to understanding the size-dependent, many-body character of nanoscale physics and chemistry. Important examples which have increased our appreciation of the different forms in which size dependence is manifest include measurements and calculations of metal cluster melting, the transition of planar to three-dimensional structures and the reactivity of gold cluster nanocatalysts. Measurements conducted in our laboratory investigate the development of cluster structures with size range to develop an understanding of how these structures evolve through intermediate sizes to achieve “magic number” structures composed of closed electronic or atomic shells. The structural symmetries of cluster ions stored within a quadrupole ion trap are probed by electron diffraction as a function of cluster size and temperature. The experimental configuration enables the accumulation of size selected clusters, collisional relaxation of the vibrational energy and adequate exposure time to collect electron diffraction data from ~104 clusters. It is precisely the ability to isolate a single cluster size having a well defined temperature which provides for a controlled investigation of quantum size effects.

Biomolecule Dynamics and Interactions Probed by Fluorescence

The three-dimensional structures and dynamics of proteins and other biomolecules play a central role in determining their unique functions in living organisms and their specific interactions with other molecules. One major challenge of life science is to grasp how a given sequence of amino acid residues gives rise to the native structure and function. We have developed a probe of the conformational dynamics of unsolvated proteins and peptides that is based on modulation of the fluorescence of a covalently attached dye through intramolecular quenching by tryptophan (Trp) or other residues. These gas-phase measurements are used in combination with solution measurements and theoretical calculations to advance our understanding of how the solvent environment affects the behavior of biomolecules and non-covalent complexes.