The action spectroscopic characterization of ion-molecule complexes can be quite tricky due to band broadening effects. To increase the spectral resolution, tagging techniques are frequently used. Tagging with helium has the smallest matrix effect and thus helps to achieve the highest quality spectra. However, He adsorption requires extremely cold conditions.

The group of prof. dr. P. Scheier works on the IR and UV spectroscopic characterization of ionic molecular complexes through tagging them with He as a messenger, which will be eliminated upon resonant photoexcitation.  In this project we will spectroscopically study the products resulting from reacting C₆₀⁺ ions with astrochemically relevant species such as H₂, D₂, H₂O, CH₄ and CO₂ within He droplets.  The droplets are stored in a collision cell, where excess helium is evaporated until the cold ion of interest is only decorated with one or a few He atoms. This technique allows for the formation of ion-molecule complexes, under very cold conditions, and the most sensitive of spectral characterization through He elimination.