What is the highest frequency gamma ray emitted by any nucleus?

[granpa]

whats the highest frequency gamma ray normally emitted by any nucleus

something that I read said that gamma rays were normally less than 10 Mev

 

[Drakkith]

I can't be sure, but I did find this on wikipedia's article on Gamma Rays.

Light interaction
High-energy (from 80 to 500 GeV) gamma rays arriving from far far-distant quasars are used to estimate the extragalactic background light in the universe: The highest-energy rays interact more readily with the background light photons and thus their density may be estimated by analyzing the incoming gamma-ray spectrums.[9]

Now, this may not be a typical example, and from everything else I've read, the normal gamma rays produced from things on Earth are indeed under 10 MeV.

 

[Borek]

http://en.wikipedia.org/wiki/Greisen–Zatsepin–Kuzmin_limit

But it has nothing to do with the energy emitted by nucleus, it just tells that we won't be able to observe higher energy gamma rays (unless they were emitted close enough), no matter what emitted them.

 

[Astronuc]

whats the highest frequency gamma ray normally emitted by any nucleus

something that I read said that gamma rays were normally less than 10 Mev

Yes - nuclear energy levels of 92 natural and about 26 artifical man-made elements and the population of radionuclides are on the order of several MeV, up to about 10 MeV.

A quick search of a tabulated database on gamma ray energies reveals:

E(keV)      Intensity  Nuclide  Decay Mode and half-life
8857(20)    0.16        B-13   (B- 17.36 MS) 
8869.3( 5)  7.600e-02   N-16   (B- 7.13 S) 
8887.5( 2)  8.600e-02   P-28   (B+ 270.3 MS) 
8966        0.109       K-48   (B- 6.8 S) 
9046.78( 7) 3.100e-02   C-15   (B- 2.449 S) 
9218.8(12)  4.920e-02   K-36   (EC 342 MS) 
9300        0.46        K-48   (B- 6.8 S) 
9379.5( 5)  2.020e-02   P-28   (B+ 270.3 MS) 
9450.1      0.11        Al-24  (EC 2.053 S) 
9477.4( 9)  5.500e-02   P-28   (B+ 270.3 MS) 
9793.8(10)  1.300e-02   P-28   (B+ 270.3 MS) 
9826.2      0.2         Al-24m (EC 131.3 MS) 
9893( 5)    2.200e-02   B-13   (B- 17.36 MS) 
9943.3      2.700e-02   Al-24  (EC 2.053 S) 
9965.6      1.6         Al-24m (EC 131.3 MS)

Apparently energy levels for elements beyond Z=111 are not yet known.

 

[bcrowell]

Gamma rays from the giant dipole resonance can be 30 MeV or more. Here's a paper with some typical spectra: http://arxiv.org/abs/1006.0557

What Astronuc's search shows is that the highest *discrete* gamma-ray energy ever measured was about 10 MeV. Re Z>111, if you want to see high-energy discrete gammas, you want to look at low-mass nuclei. This is just a particle-in-the-box thing; energies scale up in lighter nuclei, and that's why the search turned up nuclei in the A~20-30 range.

As Borek notes, very high energy gammas can be seen in cosmic rays (up to 10^13 MeV!). I don't know much about the mechanism of emission of these gammas, but they can't be emitted by a nucleus dropping from an excited state down to a lower excited state, which is what the OP seems to have had in mind.