Unfortunately, it is very difficult to measure the initial cluster formation using experimental techniques. State-of-the-art instruments such as the Chemical Ionization Atmospheric Pressure interface Time-Of-Flight mass spectrometer (CI-APi-TOF) can measure the chemical composition of the clusters. However, the ionization efficiency by different CI reagent ions (nitrate /bisulfate 27 /acetate 28 /iodide ) varies between individual atmo-spheric species and fragmentation inside the instrument also affect the detection efficiency of the clusters. Overall, CI-APi-TOF measurements only yield the chemical composition and at the moment there exist no experimental techniques to obtain direct insight into the exact cluster geometries.