How do you read a spectrum for a decaying source?

[jumbogala]

Homework Statement

I have a ¹³⁷Cs source which decays to ¹³⁷Ba. When the Ba nucleus decays, it gives off a photon which can undergo Compton scattering.

Homework Equations

The Attempt at a Solution

The spectrum shows something that looks like a saddle on the left (it has two high peaks on either end and dips down in the middle). Then on the right there is a very high, sharp peak.

The high peak that shows the full energy of the photons is showing the photons that got absorbed directly by the device. Right? It says 91.1 % of photons have that energy.

So the other ~10% must undergo compton scattering, which is the saddle thing. But what causes the high peaks on both sides of it? It has something to do with photons giving up energy to electrons. Can anyone explain, I would like to understand. Thanks!

 

[Jhero]

Hi there,

Yes, you are correct in your understanding of the two peaks in the spectrum. The high peak on the right represents the 91.1% of photons that were directly absorbed by the device. These photons have the full energy of the original 137Cs source.

The saddle-shaped peak on the left represents the photons that underwent Compton scattering. This is a process in which the photon interacts with an electron and loses some of its energy. The peak on the left side of the saddle represents the photons that lost a small amount of energy, while the peak on the right side represents the photons that lost a larger amount of energy.

The reason for these peaks is due to the different angles at which the photons interact with the electrons. When the photon loses a small amount of energy, it means that it interacted with an electron at a small angle. When it loses a larger amount of energy, it means that it interacted with an electron at a larger angle.

I hope this helps to clarify the peaks in the spectrum. Let me know if you have any further questions.