Dipolar and single-phase two-electrode quadrupolar detection schemes have been investigated at a Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) setup built for the KATRIN experiment at the Max-Planck-Institute for Nuclear Physics (MPIK) in Heidelberg. We present first experimental results of 7Li+ signals from a cylindrical Penning trap configuration for both detection schemes. While the prominent signal of the conventional dipolar detection scheme marks the reduced cyclotron frequency, the main signal for the quadrupolar detection appears at the sum of the reduced cyclotron frequency and the magnetron frequency. For ideal trapping fields, this sum frequency equals the ion cyclotron frequency ν c = qB/(2πm). Sidebands due to the combined motions of the cyclotron mode and magnetron mode are observed by quadrupolar detection which allows the determination of the respective combinations of eigenfrequencies
In a Penning ion trap the interconversion between the radial motional modes of stored particles can be accomplished by applying one- and two-pulse (Ramsey) azimuthal quadrupolar radio frequency fields. In this work the interaction of ions with the excitation fields has been probed by Fourier transform ion cyclotron resonance (FT-ICR) detection. A theoretical description of this interaction is derived by use of a quasi-classical coherent state and the interconversion of modes is interpreted in a quantum-mechanical context. The dipolar-detection FT-ICR signal at the modified cyclotron frequency has been studied as a function of the interaction parameters such as excitation frequency, amplitude and duration and is compared with the theoretical results
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