Calculation of few-line mass spectra, obtained by the modulation method

A technique of numerical calculation of mass spectra obtained by the modulation method based on the difference in initial kinetic energies of molecular and fragment ions is described. The Maxwell distribution in initial velocities of molecular ions and the Gauss distribution in initial velocities of fragment ions were used for mass spectrometer description. Theoretical calculations and experimental data for the case of O2 and H2O ionization have been compared. It is shown that modulation method can be applied in that case when it is necessary to detect small concentration of atoms in mixture with high concentration of molecules containing these atoms