Mathematical Simulation of the Mass Discrimination in Electron Ionization Mass Spectrometry and the Possibility of Its Correction

Ion mass discrimination in mass spectrometry with electron ionization is a nonremovable effect, reducing the accuracy of isotopic composition measurement, the exact knowledge of which is extremely necessary in many applications. The reason for these discriminations is the necessity to use additional magnetic field in the ion source, focusing a beam of ionizing electrons. The paper concerns the displacement of an electron beam, the ionization region, and the ion position for various masses in the ion beam during its formation in an ion source optical system, studied by mathematical simulation. Introducing voltage correction on the extraction electrode can significantly, by two orders of magnitude, reduce the discrimination.