Nuclear Physics - Difference between electron capture and beta plus decay

In summary, the conversation discusses the process of atom decay and the different modes it can occur in, specifically electron capture and beta plus emission. There is uncertainty around predicting which mode is more likely and it is suggested that for introductory physics, it is sufficient to mention both possibilities. It is also mentioned that computing branching fractions for decay modes is a complex task.
  • #1
emilypearson
7
0
So my question has a few parts to it.
First, if an atom is decaying and the proton (Z) number is decreasing in the decay process, am I correct in assuming that the nucleus is either decaying by electron capture of beta plus emission?
Secondly, I understand that beta plus emission can only occur is the mass of the original atom is at least 2 electron masses larger than the final atom. Therefore if the final mass is under 2 electron masses, the atom decays by electron capture. However, if the final mass is larger than 2 electron masses, how do you know if it is decaying by beta plus emission or electron capture?
Thanks in advance for any help.
Emily.
 
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  • #2
Hi Emily-
Cu64 is odd-odd, and decays to both Zn64 (even-even) by beta-minus decay, and by positron AND electron capture to Ni64 (even-even). See http://en.wikipedia.org/wiki/Copper-64. I think V50 is similar.
 
  • #3
Thanks, but is there any way of predicting which is more likely? For example Ce-137 (Z=58) decays by positron decay (according to a search engine). How would you know it is beta plus not electron capture? Or is there no way of working it out (via masses etc)?
 
  • #4
Cu64 decay modes show that electron capture is about 45%, meaning that only about 55% of decays emit a typical charged beta ± decay lepton with a contiunuous energy spectrum. The best signature would be to look at the unique decay neutrino energy spectrum in electron capture (LOL).
 
  • #5
So I guess for first year university physics I'm ok just to write 'beta plus and/or electron capture' and hope for the best in the exam next week! Thanks very much for your help.
 
  • #6
Yes, computing actual branching fractions, or even estimating them, is way beyond what you might be expected to do or know how to do. You might need to know how to measure these experimentally, though.
 

1. What is electron capture in nuclear physics?

Electron capture is a type of nuclear decay process in which an electron from the innermost shell of an atom is absorbed by the nucleus, resulting in the conversion of a proton into a neutron. This process occurs in atoms that have an unstable nucleus and a low neutron-to-proton ratio.

2. How is electron capture different from beta plus decay?

Electron capture and beta plus decay are both types of nuclear decay processes, but they differ in the particles involved. In beta plus decay, a proton in the nucleus is converted into a neutron and a positron (a positively-charged electron). In electron capture, an electron is absorbed by the nucleus, resulting in the conversion of a proton into a neutron.

3. Which elements undergo electron capture?

Electron capture can occur in elements with an unstable nucleus and a low neutron-to-proton ratio, such as potassium-40, calcium-40, and iron-52. These elements have an excess of protons in their nucleus, making them more likely to undergo electron capture to become more stable.

4. What is the role of the weak force in electron capture and beta plus decay?

The weak nuclear force is responsible for both electron capture and beta plus decay. In electron capture, the weak force governs the interaction between the electron and the proton in the nucleus, causing the proton to convert into a neutron. In beta plus decay, the weak force governs the conversion of a proton into a neutron and a positron.

5. How is energy released in electron capture and beta plus decay?

In both electron capture and beta plus decay, a small amount of energy is released in the form of an electron or positron. This energy is released due to the conversion of a proton into a neutron, which results in a more stable nucleus. The amount of energy released varies depending on the specific isotope undergoing decay.

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