Re: cesium-137 gamma abundance

[Bob Hearn <rah@america.net>]

Although we call it Cs-137, we are dealing with an emission from the
daughter Ba-137m whose 89.8% yield of the 662 keV gamma from 94.6% of the
decays of Cs-137 (slight variations in values amongst references) results in
a the 662 keV emission at a probability around 85% (product of the parent
and daughter decay probabilities) for the Cs-137 decay.

Bob Hearn
No affiliation
No disclaimers

At 04:40 PM 10/22/96 -0500, you wrote:
>I have a question concerning the yield or abundance for the cesium-137 662
>keV gamma.  The lesson plans used here at Los Alamos National Laboratory
>(which are written by the DOE) use the 6CEN to get the exposure
>rate in R/hr, where C is the activity in curies, E is the energy of the
>gamma in MeV, and N is the percent abundance.  The lesson plan uses 85% as
>the abundance for the 662 keV gamma and I ahve ssen the 85% used elsewhere.
>When looking in books that show the decay scheme for cesium-137 they
>indicate that the abundance is 93.5%.
>
>Which one is correct?  Any thoughts on the subject would be appreciated.
>
>Thanks.
>
>
>Rick Rasmussen
>Los Alamos National Laboratory
>phone: 505-665-7973
>fax:   505-665-4859
>e-mail rickras@lanl.gov
>
>
>