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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If greater the binding energy per nucleon, more the stability, then why is Uranium (7.7MeV/nucleon) unstable?

My book says that if the binding energy per nucleon is high, then the nucleus is stable, which is why Fe (iron), with 8.8 MeV, is most stable. Why then is Uranium unstable and subject to nuclear decay?...
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Why is helium-3 stable?

Why is helium-3 stable? Besides hydrogen, helium-3 is the only isotope that has a neutron-to-proton ratio less than 1. Why is it not radioactive?
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How does protium-protium fusion work?

How does protium-protium fusion work? As far as I know, a proton turns into a neutron by emitting a positron. How does that work? Shouldn't a proton be slightly lighter than a neutron? This seems to ...
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Why is the tritium nucleus smaller than the deuterium nucleus?

The rms nuclear charge radius of deuterium is approximately $2.1\,\mathrm{fm}$, while the charge radius of tritium is given by $1.8\,\mathrm{fm}$ although there is an additional neutron. Similarily, ...
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ISOTOPE.one of the two or more species of ATOMS [closed]

ISOTOPE, One of the two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behaviour but with different atomic ...
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Why is the alpha particle in alpha decay considered to be in a potential well?

I understand that when modelling alpha decay, it is useful to consider the $\alpha$ particle as being preformed, in a region confined to the daughter nuclei. I also understand that the term $V_{0}$ ...
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Why is residual strong force needed?

I was wondering why the residual force was needed to hold nucleons together? If the net charge resides on the surface and acts perpendicular to the surface (page I found, though not about nuclei), how ...
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What makes strong nuclear force repulsive at <.5fm? and attractive<3fm [closed]

Would it have anything to do with vector patterns they produce? Or is it like how a spring when is stretched or compressed?
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Are neutrons an actual particle? [duplicate]

I'm a senior student in high school and we are learning about Particle Physics in Physics. I wanted to ask a question about neutrons. Is there a possibility that neutrons may not even be a particle, ...
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What will be the phase of 3C-SiC when the temperature returns to ambient?

I understand 3C-SiC will likely change phase at high temperature but will the original phase still remain when the temperature returns to ambient or at ambient, the phase will still be the new one ...
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Behaviour of Nuclear Force

If nuclear force is attractive, then why the nucleons don't collide with each other? I hink about this, but do not get any proper answer?
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Why the charge of the proton does not transfer to the neutron in the nuclei?

For example, when we put two objects of +10C and +20C together and then take them apart, each of them acquires a charge of +15C. In a nucleus, the protons and neutrons are stuck together. Why is it ...
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Quick question about gluons

Gluons are exchanged between quarks of the same proton or neutron, thus keeping that proton or neutron together. But are gluons exchanged between different protons and neutrons? If so, is this what ...
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Photodisintegration of deuterium

The photodisintegration reaction is given by $$\gamma\ + d\rightarrow n \ + \ p$$ I'm trying to find out the minimum energy of gamma photon $E_\gamma$ so that the reaction can occur. Writing the ...
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Proton and neutron can't collide and form a ground-state deuteron; what happens instead?

One might expect that a proton and neutron could easily collide and form a deuteron. However, since $m_d < m_p + m_n$, the process $p + n \to d$ can't conserve both energy and momentum. For ...
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What is the precise value of the lifetime of a neutron?

Free neutrons are unstable. It decays to proton, electron and an antineutrino via beta decay. Can we not do a quantum field theory calculation to predict the precise the decay width? Its inverse ...
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Do Efimov states contribute to fusion reactions other than the triple-alpha process?

An Efimov state is a three-body quantum state in which each two-body subsystem is unbound, but the system as a whole is bound because of the large s-wave scattering length. Intuitively, one can ...
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Matrix elements of Tenser force $S_{12}$ in Spin-dependent Nucleon-Nucleon Interactions

I am aware of the fact, that the matrix elements of the tensor operator $$S_{12}= 3( \boldsymbol{\sigma}_1 \cdot \hat{\mathbf r})(\boldsymbol{\sigma}_2 \cdot \hat{\mathbf r}) - \boldsymbol{\sigma}_1 \...
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$Q$-value in Beta decay

I was reading about the mass defect or $Q$-value in Beta Decay and the book that I was following said this, It iscalled beta minus decay as negatively charged beta particles are emitted. The rest mass ...
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Binding Energy and Stability in Nuclear fission

I've read that particles in nuclear fission disintegrates into two particles with higher binding energy, and in this process energy is released. Now I am just trying to understand this by common sense,...
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What would happen if the attractive force at work in the nucleus had been equal in magnitude to the repulsive electrostatic force between the protons?

I am just starting with radioactivity and I came upon this statement: "Since the nucleus is stable, this means that there is some attractive force at work in the nucleus and that its magnitude ...
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1answer
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Stable number of neutrons for a given nucleus with $Z$ protons [closed]

I have been trying to derive an expression for the stable number of neutrons using the semi-empirical mass formula. I tried to derive it by dividing the Ma by total number of nucleons and then ...
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EM transitions - selection rules

In atomic physics we say that only transitions with $\Delta l = \pm 1$ are allowed. This is since photons are bosons. But for example in nuclear physics we also consider higher order EM transitions ($\...
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Why is aluminum more common in the solar system, etc. than sodium and fluorine?

I know that odd-numbered elements are less common than even-numbered ones, but why is aluminum more commonly created in the galaxy, apparently, than lighter odd-numbered elements? Sure, sodium and ...
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Can Uranium-238 undergo ordinary (single) beta decay?

Can U-238 undergo regular, single beta decay? Are there isotopes which can only undergo double, never single, beta decay? Not even two normal beta decays in quick succession?
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What determines whether a water-cooled nuclear reactor has a positive or negative void coefficient? [closed]

If I'm not mistaken it is the case that in water-cooled reactors the water acts both as a neutron absorber (negatively contributing to the amount of fission) and as a moderator (positively ...
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Why radius of alpha particle isn't just a number?

According to the paper recently published in Nature 589, pp. 527–531 (2021) called Measuring the α-particle charge radius with muonic helium-4 ions the root-mean-square charge radius of the α particle ...
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Inverse Square Law of Gamma Radiation Experiment

When performing this experiment with a cup source and GM Tube it says that you should start at a distance several times the diameter of the GM tube in order to obtain accurate results (https://www....
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Math in Nuclear Reactor [closed]

I don’t understand the meaning of equations in nuclear reactor physics. How do I learn the relevant content? Those complicated formulas and symbols often confuse me. How can I learn reactor physics ...
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Find the gamma decay multipole order of 40Ca

The spin-parity of 40Ca is 0+. So the first excited from the shell model is 1f(7/2) state. The gamma decay 7/2 --> 0+ is not possible. So what is the answer here? I was thinking that the first ...
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Shaped charges/explosive lenses and implosion in the Fat Man design for the Nuclear Bomb: how do these actually cause implosion? [closed]

This is gone into at some length but not much detail (that I could understand) in "The Making of the Atomic Bomb" by Rhodes. The basic story is that the Americans were having trouble getting ...
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Why is nitrogen (with 7 protons and 7 neutrons) so much more abundant than any other odd-odd isotope?

Having an even number of neutrons and/or an even number of protons tends to make a nucleus more stable against radioactive decay. There are only 5 stable nuclei with both an odd number of neutrons and ...
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How many atoms does a relativistic ion dislodge?

Given a large chunk of some hard, refractory material e.g. graphite, diamond, tungsten, at low temperature surrounded by vacuum, and an impacting relativistic ion – to be specific, say an alpha ...
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Do you know of any video lectures in nuclear and particle physics? [closed]

I was hoping the internet would be filled with video lectures since lots of universities have been forced to conduct online teaching. However, that doesn't seem to be the case. Therefore I was hoping ...
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Strange behavior of Polonium — can it be accounted for by heat and/or ionizing radiation?

I have read that Polonium does things like move against air currents or migrates within containers to (I think) different parts of the container. But I also read that a .5 gram chunk will reach 500 C. ...
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If Pu-239 is irradiated in a neutron flux, will a fizzle detonation occur? How much flux would be required?

I'm not looking for K values here, just an estimate of the external neutron flux, so I can compare it to reactor fluences.
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$E=mc^2$ Shouldn't high energy decay GAIN mass not lose it? [closed]

I feel I've hit a bit of a paradox. I've learned that alpha decay releases a lot of energy, and that energy comes from the mass of the daughter products via $E=mc^2$. But, if the decay has more energy,...
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1answer
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Why is 20% enrichment for uranium considered the minimum for making a nuke? [closed]

I get that this is the physical limit - an infinite mass of uranium would produce a runaway reaction. But an infinite mass is impossible. Really, what is the minimum % of enrichment of uranium which, ...
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Why is the mass defect of nuclei used while calculating the $Q$ value of decay reactions?

i just came across two questions today the first one goes like: Here the answer is calculated with (mass defect of nuclei)*C^2,why do we use the mass of nuclei to calculate Q value in this case  but ...
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What are the major difficulties to the production of elements?

Searching online about this topic only gives results about nucleosynthesis (making elements by nature) and the 24 radioactive artificial elements. Why isn't there any information about methods to make ...
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Why do helium fuse in the Sun?

Initially there are lots of hydrogen atoms and trace elements in the Sun. Despite insufficient energy for the hydrogen to fuse in the core, quantum tunneling saved the day and invoke proton-proton ...
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Can a nuclear reactor also experience freezedowns?

So meltdowns happen when a core gets overheated so much that it becomes very unstable, But is there a way to cool down a reactor so much to the point where it is below freezing and causes a freezedown?...
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What is the relationship between binding energy, energy released, and mass defect? [duplicate]

Im learning about fission/fusion and cant get mass defect, binding energy, and energy released to fit together in my head. The three are all equal in magnitude if I understand it correctly? When, for ...
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Positive binding energy shenanigans

In Introductory Nuclear Physics by Kenneth S. Krane, section 3.3 p.65 is presented the following formula for the binding energy of a nucleon: $$B=\left\{Zm_p+Nm_n-\left[m\left(^{A}X\right)-Zm_e\right]\...
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Do you need to account for relativistic effects for neutron-nucleus collisions in nuclear physics?

When you calculate the kinetic energy or the angle of deflection, etc, do you need to take in account relativistic effects (whether you are in the center of mass or in the laboratory system)? I mean ...
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Does the Doppler broadening in nuclear physics also change the interaction type of the particles involved?

Relative motion of the nucleus due to the temperature causes the Doppler effect broadening. But does the change of temperature also change the type of interaction, directly or indirectly? For example, ...
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What is Fermi age? What does it represent? [closed]

What does the lethargy represent? What are its units? What is the range of the lethargy? (Is it between 0 and 1?) The definition of lethargy is: $u = \ln \frac{E_0}{E}$ and the average increase in ...
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Photocell current vs light intensity calibration

In Lab experiment, to verity the inverse square radiation law, we observe the solar cell current changes with the distance from the light source. How would we relate the solar cell current and the ...
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On Nucleus-Nucleus potential for fusion reaction of light nuclei

Its know that in nuclear fusion reactions, the nucleus-nucleus potential cannot be simply given by; $V(r)=\frac{kZ_pZ_t}{r} for, r>\frac{kZ_pZ_t}{E}$ $V(r)=-U_0 , or, \frac{-U_0}{1+e^{\frac{a-r}{b}...

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