Questions tagged [nuclear-physics]

Nuclear physics is the study of the composition, behavior and interaction of atomic nuclei and their constituent parts.

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Confusion in Positron Decay

As we know, in a positron decay, by the involvement of weak forces, a proton converts into an neutron, emitting a neutrino and a positron, all of this happens inside the nucleus. Why doesn't the ...
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Why do unstable nuclei form?

Why do unstable nuclei form? Is it that we simply find unstable nuclei in nature and understand what these nuclei do in order to become more stable? I feel like textbooks gloss over this question ...
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How to deduce the total angular momentum of the ground state of a nuclide using the shell model?

So I am studying the shell model and I am having difficulties understanding the relationship between the ground state of a nuclide and its shell structure. For example, considering $^{18}_9 F$, this ...
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2answers
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Electric quadrupole and octupole moments for nuclei

I am getting slightly confused as to which nuclei cab exhibit quadrupole and octupole excitations. In This link it says closed shell nuclei cannot exhibit quadrupole oscillations because if their ...
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1answer
98 views

Scope of $E=mc^2$ [closed]

As far as I can see, Einstein's $E=mc^2$ is most often mentioned in the context of nuclear physics, even though it is more generally applicable. I understand that this is due to the large nuclear ...
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1answer
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Is the (range of the) strong force the same for nucleons and quarks?

In high school, I learnt that the strong force held the nucleus together. It had a very short range and was repulsive at small separation distances to prevent the nucleons from collapsing. Now I am ...
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Luminosity of the sun

How is it that the total power generated by nuclear reaction in the core of Sun exceeds its total luminosity? Where does the difference go?
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Question on two-neutrino double electron capture

There was a fascinating paper in Nature recently, on the observation of two-neutrino double electron capture in xenon, with a half-life time of $1.8\times 10^{22}$ years. The process described in the ...
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20 views

How to extract quadrupole moment and its error from $\chi^2 < \chi^2 + 1$ surface?

I have following info: plot of $\chi^2$ minimization of 208-Rn Coulomb excitation data, Surface corresponds to regions $\chi^2 < \chi^2 + 1$ with error bars of 1$\sigma$, mean lifetime is 8 $\pm$ 0....
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1answer
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Stability of isotopes

Yesterday I was looking at the semi-empirical mass formula and calculating some binding energies of specific nuclei. Eventually I came across this website that listed both total binding energies per-...
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52 views

Nuclei violating B number

Within SM, it is know that baryon number is not preserved and changes as $$ \Delta B = 3·\Delta n_{CS}, \quad n_{CS} \in \mathbb{Z}\ ({\rm Chern-Simons\ index\ for\ vacuum}) \tag1$$ Then, its ...
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$E = mc^2$ and Binding Energy Confusion [closed]

I have been introduced to $E =mc^2$ and binding energy recently while studying nuclear physics and I have a hard time understanding the following: Mass-Energy what does $E=mc^2$ really mean, as I ...
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Limit to number of neutrons in nucleus [duplicate]

As far as I understand the number of protons in a nucleus is limited because Coulomb forces grow faster with the number of protons than the nuclear force. So alpha/cluster decay limits the size in ...
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$2\nu\beta\beta$ vs. $2\nu$ECEC

Considering the recent observation of two-neutrino double electron capture ($2\nu$ECEC) by the XENON Experiment: https://arxiv.org/abs/1904.11002 I was wondering why the half-life of this process is ...
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Isn't it entropy (disorderliness) that every atom in the universe is not of iron Fe?

The concept of mass defect and binding energy Iron has most mass defect and the greatest binding energy. It has the most stable nuclei. Nuclei with higher atomic number than iron undergo fission ...
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What distinguishes a duoplasmatron from simpler methods of ionizing gases?

I've been looking at duoplasmatron designs and am not sure what makes the basic function of a duoplasmatron different from simply ionizing H2 gas by sending an arc discharge/electric current through ...
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45 views

Why do we observe the nuclear force only in scatterings and decays?

Why, at first glance, are the only forces we perceive to be gravity without quantizing, electromagnetism and nuclear forces only in disintegrations?
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Why is anti-neutrino produced along side with electron in beta minus decay? [duplicate]

so i get that when there is an excess of neutrons, neutron is converted into a proton. An electron is produced to neutralise the +1 charge of proton. But why is an anti neutrino produced?
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What is Incoming wave boundary condition (IWBC) in context of nuclear fusion reaction?

For calculation of fusion cross section at sub barrier energies, instead of regular boundary condition we impose Incoming wave boundary condition (IWBC). How does this different from normal boundary ...
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1answer
51 views

For which kind of nuclear reactions is the nuclear binding energy per nucleon appropriate?

The nuclear binding energy curve is often presented as a reason why iron is abundant in planet cores. However, to me it is not entirely evident why binding energy per nucleon, E/A, is chosen to assess ...
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20 views

Which books or content should I prefer to understand particle physics operator and representations [duplicate]

I am just a intermediate passout and I want to know which books should I prefer for learning the mathematics of particle physics level like the different representation, operation like Hamiltonian, ...
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30 views

Bare Critical Masses of $^{241}$Am, $^{242m}$Am, $^{238}$Pu and $^{242}$Pu

$^{238}$Pu has 144 neutrons, and it has 2.8$\times$10$^{3}$ g$^{-1}$.s$^{-1}$ spontaneous fission neutrons and bare critical mass in 10 kg. $^{242}$Pu has 148 neutrons, and it has 1.7$\times$10$^{3}$ ...
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Strange quarks in neutron stars

Recently I have read that the pressure within neutron stars can be so extreme that it can cause the deconfinement of quarks to form a kind of quark 'soup' and that these extreme conditions allow for ...
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Scaling of nuclear and electromagnetic force

The Wikipedia article on alpha decay stated: The strength of the attractive nuclear force keeping a nucleus together is thus proportional to the number of nucleons, but the total disruptive ...
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Why is the actual KE value smaller than what I calculated?

Problem The nuclear equation for the decay of calcium-47 into scandium-47 is given by: The following data are available: Mass of calcium-47 nucleus = 46.95455 u Mass of scandium-47 nucleus = 46....
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Example of calculating phase shifts in scattering theory

I have an extended question to this post: Phase shifts in scattering theory I have read it and also went over the formalism in Sakurai's, Shankar's, and Griffith's. I am now trying to look for ...
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1answer
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Fusion Kinetic Energy

In fusion, the mass of the reactants is greater than the mass of the products. Thus, mass is lost in fusion. My thinking was that this mass defect is converted into binding energy that is then used to ...
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87 views

Why do boron 11 and boron 12 isotopes have difference in stability ?(boron 11 is stable and 12 is unstable ) [closed]

Any nucleus will stable if it has neutron number= proton number. Or Even mass number=even atomic number or proton number.(maximum stability ) Or neutron number /proton number less than 1.6(not sure). ...
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Are particles that are moving at the fermi energy easier to remove if you model a nucleus as a fermi gas?

Due to the Pauli exclusion principle, the nucleons build up the energy states from the bottom up. When talking about binding energy per nucleon, you are talking about how much energy is needed to ...
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32 views

Tritium decay energy too small for quark model

So $^3$H turns into $^3$He through $\beta^-$ decay, right? The energy of this reaction is only 18.6 keV. However, according to the constituent quarks model, the only thing different between $^3$H ...
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33 views

Why does stability come from binding energy and not mass

The mass of a nucleus is given by: $$ Mc^2=n M_n c^2+zM_pc^2-B(z,n) $$ And we were told that nuclei want to maximise the binding energy per nucleon. However, I don't see why they don't want to ...
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25 views

Why is the energy taken to free neutrons irrelevant to the energy released in a fission reaction?

Our teacher is currently teaching nuclear physics and I am confused on the process of calculating the energy released in a fission reaction. An example given in class is as follows: Uranium-235 + 1n -...
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How much radiation do nuclear physics experiments expose researchers to nowadays?

I am curious about how much radiation do experimental nuclear physics researchers/students suffer in nowadays research environment. I know this may be a dumb question, but I have can found answer ...
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Why does nuclear energy level with higher j(total angular momentum quantum number) always lie below the smaller j? [closed]

Here i don't understand the reason for the energy level with j=l+1/2 lies below the j=l-1/2 .From the shell model i see this and it is also written in my book that energy level with higher j lies ...
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2answers
82 views

Gold nucleus vs. M87 surface gravity

I tried to solve this gedanken problem, but I get a nonsense solution (may be is non resoluble). Take a gold nucleus. Nuclear radius is about $R=7.2 \:\rm fm$. Consider it a solid rigid sphere (I ...
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If all we need to do is bombard with alpha particles then why can't we do nuclear fusion like that in the star?

In Chadwick's experiment, alpha particle from a source are bombarded on beryllium atom and fusion occurs to produce carbon atoms. My question is that if it is that easy to cause nuclear fusion, then ...
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15 views

What are reasonable sets of theoretical values for mass and uncertainties of quantum particles

So I have equations of $\Delta x(t)$ that involve the uncertainties of the positions of two masses at $t = 0$, uncertainties in momenta, and the masses of the particles. The equation is complex enough ...
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1answer
127 views

Is making nuclear bomb using natural uranium possible?

I know that the critical size of natural uranium metal with graphite moderator is about 27 tons "oak ridge graphite reactor". for comparison highly enriched uranium have only 17 kg critical size with ...
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If binding energy (from mass defect) is essentially the strong nuclear force maintaining the nucleus, why is it released?

I am aware that during nuclear fusion for light elements and nuclear fission for heavy elements, the resultant elements have less mass than the original reacting elements (ie the mass defect) because ...
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Spin Orbit Coupling term

I was seeing this enlightening video of DrPhysics on Spin Orbit Coupling: https://www.youtube.com/watch?v=aftOY3OkAgA&list=PLF15670EECA944A13&index=9 And I think there is a mistake. Around ...
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42 views

Mossbauer effect: neglectable recoil or absolute no recoil?

I stumbled on the Mossbauer effect. From the wikipedia article, I cannot tell for sure if the momentum of recoil is really zero, or only neglectable. From what I do (think I) understand, the ...
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2answers
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Why doesn’t the beta particle stay in the nucleus

When a neutron splits into a proton and an electron during beta decay, why does the electron fly out? Should it not stay close to the oppositely charged protons?
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Why does the nucleus not repel itself? [duplicate]

If the nucleus is densely positively charged, why don’t the protons in the nucleus repel from each other and move towards the orbiting electrons? Because each proton is not only being repelled by the ...
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2answers
60 views

Fission inside nuclear reactor

I have studied about nuclear reactors and also know their functionality.But some how i couldn't get answers for some my questions. 1) During fission reaction enormous amount of heat is produced and ...
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1answer
32 views

Why does $S_p$ increase for closed neutron shell?

I'm taking an introductory nuclear physics course in which we just covered the shell model. In that model, the so-called magic numbers arise as a consequence of there being an energy level gap due to ...
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79 views

Why is energy released during fission reactions?

If the energy released during a fission reaction is the binding energy then what energy is left to bind the nucleons together? I'm very confused if there's a better explanation on fission I'd ...
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What exactly is binding energy?

I've been reading on radioactivity but along the way I got confused, if binding energy is the amount of energy used in holding the nucleus together then why is binding energy also the amount of energy ...
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1answer
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Relaxation/thermalization of High spin nuclei

Is it practical to keep nuclei excited to high spin for long(ish) times? What mechanisms drive the relaxation of nuclear spin? Which texts would treat this subject with detail?
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Why did the Lockheed Martin compact fusion reactor failed? [duplicate]

What made the compact fusion reactor to not be compact. What assumptions did lokheed made in its simulation that showed that it could work. Can we do anything that could make it work or it is ...