Abstract: A method and apparatus for chemical ionization of analyte gas particles in a carrier gas by introducing primary ions, characterized in that the primary and product ions are accelerated by a rotating electric field orthogonal to that direction (5) in which the ions are transported towards the exit (3) of the reaction volume (1). This can, for example, reduce unwanted cluster formation without increasing the transport speed of the ions through the reaction chamber, which improves, for example, the product ion yield. The apparatus of the invention achieves this by means of N?3 rod electrodes (6) to which N AC voltages U1(t), . . . , UN(t) with N different phase positions ascending in one sense of rotation ?1, . . . , ?N are applied.

Abstract: A method and apparatus for chemical ionization of analyte gas particles in a carrier gas by introducing primary ions, characterized in that the primary and product ions are accelerated by a rotating electric field orthogonal to that direction (5) in which the ions are transported towards the exit (3) of the reaction volume (1). This can, for example, reduce unwanted cluster formation without increasing the transport speed of the ions through the reaction chamber, which improves, for example, the product ion yield. The apparatus of the invention achieves this by means of N?3 rod electrodes (6) to which N AC voltages U1(t), . . . , UN(t) with N different phase positions ascending in one sense of rotation ?1, . . . , ?N are applied.

Abstract: A device for analyzing a sample gas comprises an ion source for generating primary ions, a reaction chamber to which the primary ions produced in the ion source and the sample gas to be analyzed can be supplied in order to form product ions by chemical ionization of components in the sample gas, and an analyzer/detector unit for determining different types of ions. A reaction space in the reaction chamber, within which the primary ions supplied to the reaction chamber and the product ions produced are guided and which extends between a first end facing the ion source and a second end facing the analyzer/detector unit, is surrounded by at least two electrodes which are in the form of helices which wind round a common axis with identical pitches and are offset with respect to one another in the direction of the axis. An AC voltage is applied to each of the electrodes.