Gamma Spectrometry Forum

Hi Guys,

Can someone smarter than me explain why I am able to see the 32 keV x-ray peak in the Cs137 spectrum?

If it is the nuclear decay from Cs137 >> Ba137m >> Ba137 which causes the excitation of the electron with subsequent X-Ray, wouldn't the x-ray and the gamma ray arrive at the detector almost at the same time, and if they did we wouldn't resolve the peak right?

I assume there must be some kind of delay, but why?

Steven

Hi Steven,

Actually, you do not get any gammas from Cs137 >> Ba137m, which is a beta decay. The gammas are emitted when the excited Barium nucleus decays into it's ground state.

As far as I understand, the Ba137m decays by either emmission of a 662 keV gamma ray or by internal conversion (which yields an high energy electron and a 32 keV subsequent X-Ray when the electron shell is refilled). In both cases, the total decay energy is 662 keV. In the second case, the greater part of the energy is converted into kinetic energy of the emitted electron.

https://en.wikipedia.org/wiki/Internal_conversion
https://www.hep.wisc.edu/~prepost/407/gamma/gamma.pdf (for Cs137 decay)

Valentin

Valentin,

I see, that makes sense, if the Ba137 decays by two different processes than the x-ray and the gamma will not be simultaneous.

Thanks for the links..

Steven