Magnetron Motion and Reduced Cyclotron Frequency

Trapping of ions in a potential well implies reflection of ions between the trapping plates that induces an oscillatory motion along the z-axis the frequency (Oz of which is given by 

The magnetic field now acts by transforming the radial force component into another circular motion of the trapped ions. The total force on an ion then is 

This quadratic equation has two solutions, the first of them representing the reduced cyclotron frequency co+ 

The ICR voltage signal strength at the detector plates is inversely proportional to ion mass if the monitoring circuit is predominantly resistive, and is independent of ion mass if the circuit is predominantly capacitive [200]. Image current detection at room temperature is typically less sensitive than ion counting techniques in 

There is a correlation between the transient signal and the pressure in the ICR cell [189,199], In perfect vacuum, the orbiting motion would solely be dampened by induction, whereas in the presence of residual gas collisions will finally slow down the ions to thermal energy. As the resolving power in FT-ICR-MS is also proportional to the acquisition time of the FID signal, ultrahigh vacuum in the range of mbar is a prerequisite in the ICR cell. 

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