Paul traps resonant excitation

When used as a linear ion trap (2D trap) many of the same techniqnes nsed with Paul traps can be used with only minor modifications. Trapping of ions with selected mJz values can be achieved, as in 3D traps, by resonant excitation methods or hy methods that exploit the boundaries of the stahihty diagram. Selective ion trapping is necessary if the hap is to be used also to create fragment ions by in-hap collision induced dissociation for subsequent analysis by a Panl hap or by FTICR or time of flight analyzers. Also, particnlarly in the case of downsheam trapping analyzers, excess unwanted ions that cause space charge problems can be selectively ejected. Resonant excitation at the ions secnlar frequencies (Eqnation [6.33])... 

Stored waveform inverse Fourier transformation, technique to create excitation waveforms for ions in FT-ICR mass spectrometer or Paul ion traps. An excitation waveform in the time-domain is generated by taking the inverse Fourier transform of an appropriate frequency domain programmed excitation spectrum, in which the resonance frequencies of ions to be excited are included. This procedure may be used for selection of precursor ions in MS/MS experiments. 

Figure 2.28 Ion trap scan function. The sequence of events used to generate a mass spectrum in a typical Paul trap is shown. This sequence is typically repeated many times with the individual spectra summed or averaged to produce the final spectrum. The generic parts of the scan function shown include (1) ion injection and trapping, (2) ion relaxation/cooling, (3) auxiliary excitation for selective ejection/storage of desired ions and (4) mass-selective instability scan. The timing of the resonant excitation function is also indicated two sine waves shown indicate a first pulse for selective excitation and a second pulse for enhancing the mass selective instability scan...

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