I do need to calculate the mean free path for an ion with a radius of 9 x 10‐8 cm in pressures of 10‐8 Torr, 10‐6 Torr, 10‐4 Torr and 10‐2 Torr
There are different equations I found but the most one is λ= 1/Nσ
N gas number density which I do not know how to calculate based on radius and pressure.
And σ which is collision cross section σ =πd2
Another equation I found = 7×10−6/ r coll2 ×P(torr)
The Attempt at a Solution
I did convert radius to nm (0.9 nm) and applied the second equation
mean free path= 7×10−6/ 0.81 ×P(10-8) and so on for the different pressure
but I am not sure if this attempt is wright
These calculations are to use in the ion free path (ion mobility) in mass spectrometer instruments.