Excess of Internal Energy Caused by Inelastic Collisions

Excess of Internal Energy Caused by Inelastic Collisions 

The total collisional energy between an ion and a neutral gas atom can be calculated from Equation 49.2, in which m, m are the masses of the colliding neutral gas molecule and the ion, respectively. Elab is ths energy imparted to the ion, and Ecm is the collisional energy referred to the center-of-mass of the ion and molecule. 

For a slow ion of 1 eV kinetic energy (E, b =1) and mass iDj = 100 colliding with a helium atom (m = 4), the collisional energy E m = 0.04 eV. Only small changes in rotational energy can be expected from such low energy collisions. 

Overall Effects of lon/Molecule Collisions and the Gse of Ion Transmission Guides 

Quadmpoles or hexapoles are used as transmission guides for both slow and fast ions. In both cases, the objective is to ensure that as many ions as possible are guided from the entrance of the device to its exit. The ions are usually in transit in a straight line between an ion source and a mass analyzer. Any ions within the transmission guides that are deflected from the desired trajectory are pushed or pulled back on course by the action of the inhomogeneous RF fields applied to the poles of the guides. 

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