Das Projekt "MACSIMS II: Messung atmosphaerischer Bestandteile mittels selektiver Ionenmassenspektrometrie, ENVIRONMENT: Atmospheric trace gases, project MACSIMS (Measurement of Atmospheric Constituents by Selective Ion Mass Spectrometry)" wird/wurde ausgeführt durch: Universität Bern, Physikalisches Institut.At the Physikalisches Institut of the University of Bern a new generation of small mass spectrometer SIDAMS for the use of atmospheric research from measuring platforms as balloon gondolas or sounding rockets was developed. With the use of new technologies is was possible to improve sensitivity and mass resolution at the same time. In the project MACSIMS (Measurements of Atmospheric Constituents by Selective Ion Mass Spectrometry) it is the intention to combine the SIDAMS ion mass spectrometer with the technique of in-situ active chemical ionization in the stratosphere und to measure the altitude profiles of the concentrations of HNO3 and N2O5. Both gases play an important role in the ozone depletion processes of the lower stratosphere. Nitric acid is a reservoir of odd nitrogen, which may be depleted by condensation with water vapour and the formation of stratospheric clouds (PSC) or aerosol particles. Dinitrogen pentoxide reacts with H2O and HC1 on ice cristals or with aqueous sulphuric acid solutions. These reactions may possibly provide an important sink of NOX inhibiting the formation of C1ONO2 and resulting in higher concentrations of C1O, which can destroy ozone.