Breit-Wigner-Function and IMS-signals
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Theoretical considerations to describe the motion of ion swarms in weak electrical fields in gases at ambient pressure normally start with pulses of Gaussian form to inject ions in the drift region of the ion mobility spectrometer. The influence of the drift gas flowing contrary to the ion drift direction is mostly neglected with respect to the form of the pulse. At the Faraday-plate a superposition of the balance between energy gain between the collisions and loss by collisions with neutral molecules during the drift towards the electrode and influence of the motion of the drift gas molecules flowing contrary becomes visible in peak shape. An analytical description on the basis of Gaussian- and Breit-Wigner-Functions is presented for the single spectrum as well as for 3D-dependences within MCC/IMS with regard to the additional influence of retention time dependencies.