Strong field ionization of complex gaseous mixtures

Among the ionization techniques in mass spectrometry, photoionization stands out as a very ‘soft’ method, i.e. it causes only minimal molecular fragmentation. This, and the advantage of avoiding adducts and clustering makes it very suitable for fast and direct mass spectrometry analyses of complex mixtures without pre-separation. However, suitable light sources for single-photon ionization are technically difficult and the methods sensitivity is limited. Alternatively, laser sources allow for Resonance-Enhanced Multiphoton Ionization (REMPI), being more sensitive but restricted to specific classes of molecules (e.g. aromatics). Ultrashort laser pulses (femtosecond-laser) may help to fill this gap by delivering an enormous number of photons in a very short time (Gigawatt pulse power) that allow for (non-resonant) multiphoton ionization of any molecular target (Hamachi, A. et al., 2015; Mehdi, S. et al., 2008). The disadvantage of increased fragmentation can at least partially be compensated by elevated pressure in the ion source (Peng, J. et al., 2012). In our new fs-laser lab, we will work on advanced strong field ionization schemes for analytics of trace gases in environmental- and health-relevant questions.