Ion trap mass spectrometer simulation for multi-ions based on an exact expression for the collision probability

To predict the characteristics of ion motion in a Paul trap being used as a mass spectrometer, we calculated the ion trajectories of the multiple particles (over then 2000 particles). In order to find a more practical mass spectrum, we adopted an exact expression for the collision probability. It was found that the exact collision probability had to be considered when analyzing materials with low masses of below 100 amu. To show clearly the differences of signal shift between light and heavy masses, we chose the materials of 50 amu and 300 amu, respectively, for the simulations. It was possible to se the difference clearly for 50 amu and 300 amu, because the relative voltage shift of the mass spectrum peak of 50 amu was 10 times larger than that of 300 amu. As the He buffer gas pressure was increased above 10-3 Torr, the differnece drastically increased. When the suggested non-approximate collision probability was introduced, the shift of the mass signal ws reduced very much. This result agreed fairly well with the experimental obsrvations