Photoelectron spectroscopy of mass selected anions is a routine method to obtain information on the electronic structure of isolated species. For many large molecular ions, which can be transferred from solutions into gas-phase by means of the electrospray method, there is an added complication: multiple non-interconverting conformers with different electronic and geometric structures. Sorting out the often overlapping spectra requires conformer separation prior to photodetachment. We realize this in a presently unique instrument which comprises an ion mobility drift cell coupled to a magnetic bottle photoelectron spectrometer. The systems of present interest include multiply negatively charged biomolecules such as DNA oligonucleotides and proteins which we study as a function of charge state and sequence to learn about the relation between charge localization and molecular geometry.
"Combining Ion Mobility Spectrometry, Mass Spectrometry, and Photoelectron Spectroscopy in a High-Transmission Instrument”, Matthias Vonderach, Oli T. Ehrler, Patrick Weis and Manfred M. Kappes, Anal. Chem., 2011, 83, 1108–1115