Parameters Influencing Ion Intensities for Quadrupole SIMS Instruments

It is well known that quadrupole mass spectrometers can be operated in various resolution modes, for example, constant ΔM or constant M/ΔM. This property is easy to understand theoretically from the stability diagram and from the equation for the scan line: (1) $${\rm{U = \alpha V}} \pm {\rm{\gamma }}$$ and the equation for the resolution: (2) $$\frac{{\rm{M}}}{{\Delta {\rm{M}}}} = \frac{{\rm{C}}}{{0.16784 - {\rm{U/V}}}}.$$ In these equations U and V are the d.c. and a.c. potentials aoplied to the electrodes, α and γ are constants determined by adjustments on the guadrupole control and C is a constant that depends on peak shape. From these equations and the fact that V is proportional to M,it can be seen that if α = 0.16784 and K ≠ 0 ΔM will be constant. Also if K = 0 and α ≠ 0.16784 M/ΔM will be constant.