Fourier voltage oscillation

The conversion of an oscillating electric field E(t), the so-called time domain spectrum, into a frequency domain spectrum is known as a Fourier transformation. A simple but neat description of this transformation is given by Hollas [16]. The oscillating electric field arising from a molecular emission line following the radiation pulse is converted into an oscillating voltage f(t) with a frequency v, which we may write... 

Veiy often, f(v) and /(f) are used to denote the forward and inverse Fourier transforms, respectively. As described in Chapter 5, Section 4, IJ(co) is the Fourier transform of the applied AC voltage U (f), and I (or) is the Fourier transform of the current response 1 (f). We write the transform in terms of the angular frequency co = 2nv instead of the oscillation frequency v ... 

In the Fourier transform ion cyclotron resonance (FT-ICR) spectrometer s,10"24 the cyclotron motion of ions of many different masses is excited essentially simultaneously (see Figure 2). The presence of excited cyclotron motion is then detected as the alternating voltage (Equation 2) after the exciting oscillator is turned off. Thus, unlike the conventional ICR spectrometers in which ion excitation and ion detection are simultaneous, ion excitation and ion detection in the FT-ICR spectrometer are temporally distinct. 

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