The combination of a widely tunable infrared laser source with tandem mass spectrometry enables the routine recording of IR spectra of gaseous molecular ions. With the aid of theoretically predicted vibrational spectra, these IR spectra can be used to derive molecular structure information on the ionized species. As an example, the sites of protonation, deprotonation or metal ion attachment in a molecule can be accurately determined using “infrared ion spectroscopy” (IRIS). The application of IR free electron lasers in this method, originally developed at the former FOM Institute Rijnhuizen, exploits the wide wavelength tunability of an FEL, which has turned IRIS into one of the prime structural methods in current ion chemistry.
With the relocation of FELIX to Radboud University and the installation of a new tandem mass spectrometry platform, funded by an NWO-VICI grant, about five years ago, new venues in ion spectroscopy appeared on the horizon. We have particularly pursued new opportunities in the characterization of ion reactions induced by collisions or by recombination. Moreover, analytical applications in the identification of unknown molecular structures of compounds in complex mixtures, such as in blood plasma or urine samples, have also been successfully explored.