Identification of analytes by an ion mobility spectrometer with formation of dimer analytes

A method for spectroscopy with charged analytes, comprising at least the following steps:

• introducing a gas sample comprising a gas mixture into a reaction space;
• carrying out an ionization process in the reaction space to create charged analytes by letting an ionization pulse I act for a time interval Δte on the gas mixture;
• subsequent carrying out of a transfer process by letting an ion extraction pulse F act for a time interval ΔtF on the charged analytes in the gas mixture by which the charged analytes are taken by the extraction field produced from the ion extraction pulse F from the reaction space into a drift space;
• drifting of the charged analytes in the drift space to a detector by means of a drift field present in the drift space and obtaining analyte signals from the analytes reaching the detector, wherein at least 3 measurements are performed and spectra recorded for one gas comprising analytes, wherein the spectra give the intensity of the analyte signals versus the drift time and for measurement to measurement the residence time in the reaction space ΔtRn is changed between the start of the ionization pulse I and the start of the ion extraction pulse F,
• wherein the peaks of the analyte signals of the various measurements are compared and each time falling and rising peak heights of a particular drift time are ascertained with respect to the peaks of the measurement with smaller ΔtRn relative to the peaks of the measurements with larger ΔtRn, the peaks of a particular shorter drift time with falling peak height are classified as the analyte signal of a monomer analyte ion and the peaks rising in intensity of a particular longer drift time are classified as a dimer analyte ion.