What Causes the Unique Scattering Patterns in the Ramsauer–Townsend Effect?

[shinwolf14]

I am currently about to do this experiment in my lab class. I had a couple of questions as I was reading over papers on the experiment:

1) Why is it classically that the scattering of the electrons decrease monotonically when velocity increases? All of the papers and websites mentioned it, but didn't explain it.

2) Why is there only one minimum? More specifically, is this fundamental to the Xenon gas (or noble gases)? If we used say, an Iodine gas, would we still get one minimum or even a minimum at all?

I haven't started the experiment yet but I would like to have a deeper understanding of the concepts before I begin. Thanks for all the help in advance!

 

[azntoon]

1) The monotonic decrease in the scattering of electrons is due to the fact that as the velocity of the electrons increases, they are more likely to pass through the gas atoms without experiencing a collision. At higher velocities, the probability of colliding with an atom is low since the energy required to cause a collision is greater than what the electron has. 2) The single minimum results from the fact that the probability of scattering decreases with increasing velocity, as explained in answer 1. This behavior is typical of noble gases such as xenon, but may be different for other gases. For example, iodine gas may produce multiple minima.