A Time of Flight Mass Spectrometer is a powerful tool utilizing electric fields to determine the mass of ions emitted/ejected from the surface of a sample. As shown in figure 1 below, a laser can be focused onto a sample of ejected ions can be accelerated by an electric field to a high transparency grid after which they continue with a constant velocity to the detector.
If the sample -> grid distance is 10mm and a potential difference of 50 volts is applied between them,
(i) calculate the electric field accelerating the ions.
If negative ions are to be detected as n figure 1 and the grid is grounded.
(ii) what is the potential of the sample with respect to ground?
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Expert's answer
2020-11-24T05:53:13-0500
i) Electric field∣E∣=dΔV
∣E∣=10×10−350V/m
⇒∣E∣=5×10−3V/m
ii) Potential of sample with respect to ground is 50V because grid is grounded.
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