Electron Impact Ionization Cross Section --> Ionization Probability

[physoox]

Hello all,

i ionize neon in a Wiley-McLaren time of flight ion mass spectrometer. That means all the ionized neon ions are detected by the detector.  Now i have calculated the number of ions from the oscilloscope trace.  But my final goal is to calculate the actual number of ions present in the interaction zone (because not every neon atom is ionized).

Can this be done with electron impact ionization cross section?

Is the electron impact ionization cross section the same as the ionization probability?
 

 

cheerz

[exchemist]

Hello all,

 

i ionize neon in a Wiley-McLaren time of flight ion mass spectrometer. That means all the ionized neon ions are detected by the detector.  Now i have calculated the number of ions from the oscilloscope trace.  But my final goal is to calculate the actual number of ions present in the interaction zone (because not every neon atom is ionized).

 

Can this be done with electron impact ionization cross section?

 

Is the electron impact ionization cross section the same as the ionization probability?

 

 

cheerz

I'm rusty on the exact meaning of cross-section and I think you are right to ask the question. As I recall, the cross section is certainly proportional to the probability of ionisation, but I have an idea it may apply at the level of each individual electron-atom interaction, i.e. the probability that a given interaction will result in an ionisation.  If that is right, then one would need to somehow allow for the fact that a lot of electrons will "miss" atoms entirely and somehow integrate over the whole population, before arriving at a proportion of the beam that is ionised. In other words, all the factors that determine the "efficiency" of a particular experimental setup in bringing electrons into contact with the atoms to be ionised.

 

But it is all too long ago for me to help very much, I'm afraid.  

Edited November 3, 2018 by exchemist

[GAHD]

...The neon atoms wouldn't move unless they were ionized, it's the charge that allows/forces them to move for TOF, right? Neon that wasn't charged wouldn't be accelerated much, just pulled by parasitic drag on the other accelerated atoms altering your mass number at the end(showing higher).