Cause of Bump in Uranium Gamma Spectrum

[eXorikos]

Homework Statement

What is the cause for the bump in the lower energies of this spectrum: http://en.wikipedia.org/wiki/File:Gammaspektrum_Uranerz.jpg

The Attempt at a Solution

Is it just normal Compton? I'm doubting that because that is very asymmetric. I can't find anything in any textbook I own. And if it's Compton, why is it so asymmetric? Is that because there are low intensity, low energy gamma peaks?

 

[eXorikos]

*bump*

 

[eXorikos]

Seriously nobody that can answer this question? :s