Kinetic energy of the ions

As with the quadmpole ion trap, ions with a particular m/z ratio can be selected and stored in tlie FT-ICR cell by the resonant ejection of all other ions. Once isolated, the ions can be stored for variable periods of time (even hours) and allowed to react with neutral reagents that are introduced into the trapping cell. In this maimer, the products of bi-molecular reactions can be monitored and, if done as a fiinction of trapping time, it is possible to derive rate constants for the reactions [47]. Collision-induced dissociation can also be perfomied in the FT-ICR cell by tlie isolation and subsequent excitation of the cyclotron frequency of the ions. The extra translational kinetic energy of the ion packet results in energetic collisions between the ions and background... 

The electric fields in such instruments are used to focus the fast-moving ion beam according to the kinetic energies of the ions contained in it. This property allows ions of individual m/z values to be focused sharply before or after deflection in the magnetic field. 

Fragmentation occurs because the repeller voltage increases the kinetic energy of the ions, not only making collision-induced dissociation (CID) more likely but also allowing endothermic ion-molecule and solvent-switching reactions to occur. 

The impact of an ion beam on the electrode surface can result in the transfer of the kinetic energy of the ions to the surface atoms and their release into the vacuum as a wide range of species—atoms, molecules, ions, atomic aggregates (clusters), and molecular fragments. This is the effect of ion sputtering. The SIMS secondary ion mass spectrometry) method deals with the mass spectrometry of sputtered ions. The SIMS method has high analytical sensitivity and, in contrast to other methods of surface analysis, permits a study of isotopes. In materials science, the SIMS method is the third most often used method of surface analysis (after AES and XPS) it has so far been used only rarely in electrochemistry. 

This example demonstrates some of the dangers which beset the use of mass spectroscopy to determine bond enthalpies in systems of this kind. In general, if the excitation energy and excess kinetic energy of the ions produced by electron impact... 

Argon neutrals are the dominant species in the plasma and collisions with these species will cause all the ions to travel at the same velocity, approximately 2.5x10 cm s through the MS interface. Therefore the kinetic energy of the ion beam will be controlled by the mass of each ion based on the relation ... 

Fig. 2a displays the ion time-of-flight (TOF) distribution obtained when (n) = 1.6 104 Xe clusters interacted with a Fourier Transform-limited 100 fs 800 nm, 1015 W cm 2 laser pulse. The TOF displays a number of peaks corresponding to ions up to Xe1,+. The peaks in the TOF are quite broad, and even display a double peak structure due to the fact that ions are emitted in forward-backward directions with respect to the detector. Both the charge state reached and the kinetic energy of the ions are signatures of collective effects in the cluster ionisation. For example, when only atoms were present in the atomic beam, the maximum charged state reached was 4+. 

Figure 17.3 Energy loss rate as a function of thickness for a 40Ar projectile in beryllium metal is shown on the scale to the right for an ion that enters the foil at the very high energy of 8 GeV. The remaining kinetic energy of the ion is shown on the left scale. Note that the ion penetrates approximately 21 mm into the metal.

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