Mass peak shape of the linear ion trap with cylindrical rods at quadrupolar resonance excitation of the confined ions

Linear ion trap excitation contour with round rods is studied by the numerical method in dependence of geometrical parameter γ = r / r 0, where r is the rod radius, r 0 is a radius of the inscribed circular between rod tips. The quadrupole resonance parametric excitation of the ion oscillations by three methods: (a) auxiliary RF voltage, (b) amplitude and (c) frequency (phase) modulation of the applied RF voltage have been studied. It was obtained that irrespective of the above methods the peak shape is symmetrical and has a slow peak tails for ratio r / r 0 = 1.12-1.13 thus the resolution determined at half peak height is the same as for pure quadrupole field.