Biomedical subjects
Publications and source records attributed to Roland Fromherz.
We demonstrate the isomer-resolved spectroscopy of gas-phase ions, with different geometries separated prior to spectroscopic probe using ion mobility techniques. Specifically, ring and chain isomers of carbon cluster anions with 10;-12 atoms have been separated by ion mobility/mass spectrometry and examined by photoelectron spectroscopy. This methodology should also apply to other ion spectroscopies, including IR photodissociation.
Small clusters have a range of unique physical and chemical phenomena that are strongly size dependent. However, analysis of these phenomena often assumes that thermodynamic equilibrium conditions prevail. We compare experimentally measured and ab initio computed photoelectron spectra of bare and deuterated silicon cluster anions produced in a plasma environment. We find that the isomers detected experimentally are usually not the ground-state isomers, but metastable ones, which indicates that cluster relaxation is strongly limited kinetically by a dwell time that is much shorter than the relaxation time. We show that, under these conditions, the highest electron affinity replaces the traditional lowest total energy as the appropriate criterion for predicting isomer structures. These findings demonstrate that a stringent examination of non-equilibrium effects can be crucial for a correct analysis of cluster properties.