# Binding energy and excited nucleus question

bonbon22
Homework Statement:
gamma radiation is Formed when a nucleus is excited.

by a particle being given off in a decay.

The excess energy caused by the change in mass defect

is converted into a photon of the same size as the nucleus.
Relevant Equations:
no equations
this is from a website on why gamma rays are released what i don't understand is, why is the mass defect lead to a gamma radiation to be formed. If the nucleus is excited and dexcites the change in energy levels would cause a photon to be released. yet here it says the mass defect is the source of energy where i thought it would be for the binding energy.

Mentor
The mass defect is a measure of binding energy released.

bonbon22
bonbon22
The mass defect is a measure of binding energy released.
but the nucleus in this case just goes down an energy level, does that mean the binding energy is released??

Mentor
Often during radioactive decay of a parent nucleus, the daughter nucleus created is in an excited state and quickly drops down and emits a gamma ray photon. The energy of that photon can be accounted for by the mass defect of the nuclei (which is a measure of binding energy released).

But show us the link that you saw and maybe things can be clarified further.

bonbon22
bonbon22
Often during radioactive decay of a parent nucleus, the daughter nucleus created is in an excited state and quickly drops down and emits a gamma ray photon. The energy of that photon can be accounted for by the mass defect of the nuclei (which is a measure of binding energy released).

But show us the link that you saw and maybe things can be clarified further.
http://www.antonine-education.co.uk/Pages/Physics_5/Nuclear_Physics/NUC_03/nuclear_3.htm

why is it equal to the mass defect?? would the mass defect not be used to hold the nucleus together or are you saying the energy level difference is equal to the binding energy of the nucleus

geoelectronics
bonbon22
http://www.antonine-education.co.uk/Pages/Physics_5/Nuclear_Physics/NUC_03/nuclear_3.htm

why is it equal to the mass defect?? is binding energy not the energy requierd to hold the nucleaus together or is it the energy released when a nucleus decays

Mentor
Several things going on here. Is the mass of an excited nucleus greater than that of a nucleus that has dropped down to the ground state? Yes. And that mass difference will equal the energy of the emitted gamma photon (and the recoiling nucleus).

But I would not use the term "binding energy" for that. That term describes the energy needed to break up the nucleus. The "mass defect" between parent nuclei and the daughter nuclei (and other particles) will equal the energy released in the decay process (fission, for example).

The two things are related, of course, since mass-energy is conserved.

bonbon22
bonbon22
Several things going on here. Is the mass of an excited nucleus greater than that of a nucleus that has dropped down to the ground state? Yes. And that mass difference will equal the energy of the emitted gamma photon (and the recoiling nucleus).

But I would not use the term "binding energy" for that. That term describes the energy needed to break up the nucleus. The "mass defect" between parent nuclei and the daughter nuclei (and other particles) will equal the energy released in the decay process (fission, for example).

The two things are related, of course, since mass-energy is conserved.
i see so in radioactive reactors where fission takes places does the neutrons collliding with nucleons, make the daughter nucleus excited then it dexcites and that's what causes the energy from nuclear fission. not the release of the binding energy of the nucleus ? sorry very last question.

Homework Helper
The phrase "release the binding energy" paints a picture of binding energy as a pool of energy that could be "released" if the nucleus were to be completely broken apart into its constituent nucleons.

But binding energy is not a pool of energy. It is a deficit of energy. It cannot be released. Instead, it must be provided if the nucleus is to be completely disassembled.

bonbon22 and Doc Al
bonbon22
The phrase "release the binding energy" paints a picture of binding energy as a pool of energy that could be "released" if the nucleus were to be completely broken apart into its constituent nucleons.

But binding energy is not a pool of energy. It is a deficit of energy. It cannot be released. Instead, it must be provided if the nucleus is to be completely disassembled.
Cheers for the reply, one more question
https://www.ocr.org.uk/Images/471908-question-paper-unit-h556-02-exploring-physics.pdf24 A right near the end
there is energy relased in this reaction of nuclear fusion but they want the binding energy per nucleon
does that mean the binding energy released, as a gamma photon, per nucleon of the hydrogen atom and not the binding energy which holds the 2 H hydrogen atom together per nucleon ? Essentially what I am asking is , is the mass defect or the " binding energy released" EQUAL to the binding energy which holds the nucleons together as this question phrases it. And does this apply to all decays essentially , i can see the contrast with fission reactions where it releases less energy.. just want to confirm if my train of thought is correct also ... cheers