Abstract
Ion orbits in the quadrupole field were analyzed for four stability zones near the original point in the Mathieu diagram displayed by the (q, a) plane. The coefficients of the Fourier series indicating the ion orbits were calulated and the angular frequency spectra of the orbits were obtained for respective zones. The approximate formulae of the orbits were also obtained at the conditions near the tip in each zone. The harmonic components in the obtained spectra increase with increasing q and a values.
