IonSense DART
In the DART ion source, a stream of helium is ionized in an electrical discharge.
Some of the helium atoms are excited electronically; the ions are sorted off and there is then a “beam” of excited helium atoms with a controllable temperature.
The sample is located immediately outside the entrance of the mass spectrometer’s spray chamber. When the excited helium atoms hit the sample, a cascade of reactions occurs, involving, inter alia, the water vapor naturally found in the air.
Hereby protonized water molecules (H3O + and clusters thereof) are formed which react with the sample by chemical ionization, i.e. typically by transfer of a proton to form M + 1 ions.