There is a limited number of methods that provide detailed chemical information on analytes in the gas phase. With conventional mass spectrometry only limited structural information can be obtained.
In contrast, infrared spectroscopy provides structural information. Unfortunately, the direct observation of an infrared photon by dilute analytes in the gas phase is not feasible. It is however possible to link this absorption event to a change in mass, such that it can be followed by mass spectrometry. The combination of these two techniques, valuable insight in the nature of ions in the gas phase can be gained.
To realize this combination, a custom FT-ICR mass spectrometer, equipped with a cryogenically cooled ion trap is built in our group. The ions trapped by this instrument are cold enough to form complexes with neutral gas particles. These complexes can be vibrationally excited by photons provided by an infrared laser system. Using mass spectrometry, it is possible to follow the mass change upon loss of neutral tags, which is triggered by the absorption of infrared photons and the following energy redistribution. Spectra obtained by this infrared action spectroscopy approach usually contain information equivalent to infrared spectra of isolated ions, making this technique the gold standard for molecular structure identification in the gas phase.