Kinetic Energy of Ions

When a charged particle traverses in the direction of an electric field, it experiences acceleration, as is the case when ions travel in the accelerating region of an ion source. The kinetic energy of the accelerated ion is given as 

---

Figure 10. Comparison of the velocity dependence of the disappearance cross-section of CHa+, formation cross-section of CH0 +, and Langevin orbiting collision cross-section, all as a function of reciprocal average kinetic energy of ions in the mass spectrometer source...

With these ends in view, one of the principal objectives of research in ion-molecule reactions is to determine the dependence on ion kinetic energy of ion-molecule reaction rates. In the classical measurements of... 

Magnetic sector mass spectrometers accelerate ions to more than 100 times the kinetic energy of ions analysed in quadrupole and ion trap mass spectrometers. The higher accelerating voltage contributes to the fact that ion source contamination is less likely to result in degraded sensitivity. This is particularly important for analysis that requires stable quantitative accuracy. 

The Lozier tube, illustrated in Figure 3, has been used by several groups for a variety of different studies, including the determination of appearance energies and kinetic energies of ion fragments produced in electron impact-induced dissociation... 

Early studies on the determination of the kinetic energy of ions have been discussed by Field and Franklin (1957c), and more recently the subject has been considered further (Olmsted et al., 1964 Dorman, 1965b). 

Excitation events can be used to increase the kinetic energy of ions, or to eject ions of a given mass-to-charge ratio from the cell by increasing the orbital radius until ions are lost by collisions with the cell plates. The background pressure of an... 

Mass Resolution In TOF-MS, mass resolution is related to the temporal width of the isomass ions packet when that packet arrives at the detector (i.e., R = t/At). In the ion source, ions are accelerated out of the source region with inherent dispersion in time (instant of ion formation), space (location of ion at the time of acceleration), and velocity (owing to differences in the initial kinetic energy of ions). These are the three primary factors that limit the resolution in a TOP instrument [11, 13, 16]. The initial kinetic energy (KE) of ions (i.e., KE before acceleration) is given by KE = where no is the initial velocity, which will be in a random direction after acceleration, KE = gV + mvl. The temporal dispersion creates uncertainty in the ions arrival time at the detector. The contribution of this factor can be minimized by the use of a very short ionization pulse and/or a fast-rise ion-extraction pulse, and also by increasing the flight path. Multiturn and multipass research TOP mass spectrometers are available to... 

Substituting for v provides a relation between the mass-to-charge ratio and the magnetic field and kinetic energy of ions at the entrance of the magnetic sector ... 

As mentioned above, there is no additional force applied to the system, and therefore the kinetic energy of ions owing to their thermal motion is expected to be much greater than their electrostatic energy, i.e., kT 1... 

---