Storage frequency modulation

Pulsed-force mode AFM (PFM-AFM) is a method introduced for fast mapping of local stiffness and adliesion with lower required data storage than recording force-distance curves at each point on the x-y plane [115]. A sinusoidal or triangular modulation is applied between the tip and sample (either via lever or sample piezo) at a lower frequency than that of either the piezo or cantilever resonance frequency. Tip and sample then come... 

Scans based on resonant ejection may either be carried out in a forward, i.e., from low to high mass, or a reverse manner. This allows for the selective storage of ions of a certain m/z value by elimination of ions below and above that m/z value from the trap. Thus, it can serve for precursor ion selection in tandem MS experminents. [156,158] Axial excitation can also be used to cause collision-induced dissociation (CID) of the ions as a result of numerous low-energy collisions with the helium buffer gas that is present in the trap in order to dampen the ion motion. [150,156] A substantial increase of the mass range is realized by reduction of both the RF frequency of the modulation voltage and the physical size of theQIT. [154,159,160]... 

Fig. 9. Schematic diagrams of the major components of cw and pulsed EPR-ENDOR instruments. The sample is in a resonant microwave cavity, situated between poles of a magnet and surrounded by a temperature-control system (not shown). The structure of the circulator directs microwaves from the source to the cavity, and from the cavity to the detection system. A radio frequency synthesizer provides rf to coils situated around the cavity. Note that this diagram shows an arbitrary orientation of the rf coils. For convenience the magnetic field modulation coils are not shown for the cw spectrometer. For the pulsed EPR spectrometer (B), fast switches (ovals) are used to control pulse timing for the rf and microwave pulses, as well as to protect the detector. For simplicity, several features including the timing circuitry are not shown. The signal from the detector is sent to a boxcar integrator. Both spectrometers are computer-interfaced for data collection and storage. Further details may be found elsewhere.

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