I am designing a simple Mass Spectrometer.

I need to find radius of $Pb_{204}^{-}$ when deflecting. I have this equation:


I know everything in that equation except the mass. I have


How can I find the mass for the equation?


The mass of a neutral $Pb_{204}$ atom is given right in your green image.

Because you have a negative $Pb_{204}^-$ ion, you need to add the mass of one electron.

  • $\begingroup$ @jmh I don't see how the radius of the nucleus is relevant here. The radius $R$ in the asked question is the radius of the curved ion beam when flying through the magnetic field in the mass spectrometer, typically a few inches. $\endgroup$ – Thomas Fritsch Jun 11 '20 at 17:39
  • $\begingroup$ you are right. my bad. Thank you! $\endgroup$ – Natsfan Jun 11 '20 at 19:31

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