Re: Cobalt-60

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

> Does decaying Cobalt-60 usually give off _both_ a 1.17 MeV gamma and a 1.33
> MeV gamma?  We use Co-60 in an experiment to measure the half-value layer
> of Aluminum for those gammas, and I'm not quite sure what the right answer
> is if I don't know the relative frequencies of the two energies.
>
> Thanks,
> Larry

Check the HB of Chem & Phys. In the table following the table of the
isotopes is one titled Gamma energies and intensities of
Radionuclides. My edition shows that Co-60 does give both of the
gammas you mention. It would appear to be a two step transition to
the ground state of the daughter nuclide, Ni-60--the relative
intensity of both gammas is listed as very near 100%.

From my old edition of the AIP HB, the Q value for Co-60 is given as
2.82 Mev, and the max beta energy is only .315 Mev (most of the
time), and the two gammas you quote add up to the rest of the stated
Q-value. There are a couple of other combinations, but they occur
less than 0.2% of the time, so they probably can be neglected.

To summarize, yes, they are both given off every time (for all
practical purposes).

Hugh
--

Hugh Haskell
<mailto://hhaskell@mindspring.com>

Let's face it. People use a Mac because they want to, Windows because they
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