Why only gamma radiation....?

PhysicoRaj

All the radioactive elements emit either alpha, beta, never both and maybe sometimes gamma with these. But why do they emit gamma rays only? Why not X-Rays?

M Quack

In principle there is no difference between gamma- and X-rays. Both are "just" electromagnetic radiation. The convention is to call them gamma when they come from the nucleus, and x-rays when they come from electronic transitions.

cmb

Quote by PhysicoRaj

All the radioactive elements emit either alpha, beta, never both

I'd not be surprised if that is generally the case because a nucleus is unstable either beause it is 'neutron heavy' and is prone to emit a beta (a beta is usually from a proton decaying, mediated by the weak force), or 'proton heavy' in which case it will emit a positron or 'it could reduce' the relative p:n ratio by lumping out an alpha.

But I'm pretty sure there are isotopes that emit all types. U238 I seem to recall decays by alpha, double beta and fission.

Vanadium 50

Ta-180 is predicted to decay via gamma emission. However, the half life is about 10¹⁵ years, and it has not been observed. There are other gamma-only states, but they typically have half-lives that are milliseconds or smaller. Since there is a huge gap, there aren't many isotopes one is likely to be familiar with.

PhysicoRaj

Thank you guys.

kurros

Just for curiosities sake, there are some freaky low energy nuclear transitions like this: http://www.thorium.at/?page_id=4. There is an isomer of Th-229 with an energy only 7.6 eV above the ground state, so when this state relaxes it emits a "gamma ray" of only UV wavelength.

*Bob S*

Historically, the term x-ray sometimes applied only to photons from atomic level transitions (up to about 120 keV), and gammas only from nuclear transitions. Now, the term x rays seems to apply to both atomic and nuclear photons.

The decay of beryllium-7 to lithium-7 is a very interesting nuclear decay, in that it emits only an atomic x-ray and a neutrino. Be-7 decays by capturing an electron from the atomic k-shell, and emitting a neutrino. It emits no nuclear gammas and no charged particles (alpha or beta). The x-rays come from outer atomic electons cascading down to fill the k-shell vacancy.

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PhysicoRaj	Why only gamma radiation....? Tweet All the radioactive elements emit either alpha, beta, never both and maybe sometimes gamma with these. But why do they emit gamma rays only? Why not X-Rays?

M Quack	In principle there is no difference between gamma- and X-rays. Both are "just" electromagnetic radiation. The convention is to call them gamma when they come from the nucleus, and x-rays when they come from electronic transitions.

Vanadium 50 Mentor	Why only gamma radiation....? Ta-180 is predicted to decay via gamma emission. However, the half life is about 10¹⁵ years, and it has not been observed. There are other gamma-only states, but they typically have half-lives that are milliseconds or smaller. Since there is a huge gap, there aren't many isotopes one is likely to be familiar with.

kurros	Just for curiosities sake, there are some freaky low energy nuclear transitions like this: http://www.thorium.at/?page_id=4. There is an isomer of Th-229 with an energy only 7.6 eV above the ground state, so when this state relaxes it emits a "gamma ray" of only UV wavelength.