Questions tagged [nuclear-physics]

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

Filter by
Sorted by
Tagged with
5
votes
1answer
58 views

Relation between isospin invariance and charge independence

I don't know if this question is better suited for this forum or math.stackexchange.com. I come from a mathematical background and I'm struggling to understand a passage in Lipkin's book "Lie groups ...
1
vote
1answer
26 views

What is residual interaction physically?

In any nuclei, if it is even-even or odd-even we can determine ground state spin and parity just by single particle shell model. But if in a odd-odd nuclei, we consider residual interaction to ...
0
votes
2answers
51 views

Why nuclear binding energy influence mass?

I do understand this from a energy point of view. However, let's consider a system with two small mass point in a classical case. The total mass of the system should be $M=m_{1}+m_{2}-\frac{E}{c^{2}}$ ...
0
votes
0answers
17 views

Neutron Multiplication Factor K [closed]

What was the neutron multiplication factor K for the super-critical mass in the Little Boy uranium bomb and also the K factors for the two sub-critical masses before the detonation?
0
votes
0answers
14 views

Natural and man-made nuclear transitions [duplicate]

I am currently studying nuclear physics, but in this concept, I could not find any related topic for this on the internet. Can someone suggest any references?
0
votes
1answer
24 views

Binding energy in nuclear fission

As far as i know, in a nuclear reaction we "go" from a binding energy $B_1$ to a binding energy $B_2$ with $B_2$>$B_1$ because a bigger binding energy means more stability for the nucleus. If we ...
1
vote
2answers
47 views

Spontaneous fission

Considering that the spontaneous fission rate of uranium 235 is 0.00563 fissions per Kg per second, why does this not cause small explosions or "fizzles" of the sub-critical fuel mass(s) in an atom ...
0
votes
1answer
33 views

Thermal neutrons and fission

In an answer here I read: You need slow neutrons because if the neutrons are too "quick" then they scatter of the atoms instead of being captured by them. You can imagine a big lump of playdoh and ...
-1
votes
2answers
46 views

Could A Stray Radioactive Particle Collide With an Atom in a Human, Causing a Cascade?

I'm not thinking of even particles from a nuclear power-plant or man-made event. If a high-velocity highly-interacting particle made it through all the natural protections that keep life in a non-...
0
votes
1answer
17 views

Stellar nucleosynthesis

I would like to learn more about fusion in stars. The question I have is whether there exists a graph showing exactly which elements take part in the reactions. Here, I managed to find some data ...
0
votes
0answers
14 views

Energy Losses at Thin Layers through Ionization

I want to approximate the energy loss of charged particles through a very thin film (low-density material). The charged particles are in the low energy range ($<$MeV). I found a formula but do not ...
0
votes
0answers
24 views

Heavy charged particle collisions with electrons of relatively large energy

I am told that, when a heavy charged particle passes through a substance, some (small number of the) collisions occur with electrons of relatively large energy. I am then told that the maximum energy ...
0
votes
2answers
24 views

Questions about a heavy charged particle passing through a substance

I am told that, when a heavy charged particle passes through a substance, ionization occurs. I am then told that the most probable occurrence is collision with an atomic electron. Finally, I am told ...
1
vote
1answer
31 views

What is a “multicharge nuclei”?

When doing some reading on particle physics, I came across the concept of a "multicharge nuclei". A Google search of this phrase returns a number of research papers, but no definition for what a "...
1
vote
1answer
24 views

$\beta^-$ and $\beta^+$ $Q$ value issue

It's unclear to me why the following doesn't work when I calculate the $Q$ value for $\beta^-$ and $\beta^+$ decay. If we start with a parent nucleus $P_z$ with $Z$ electrons decaying through $\beta^-$...
1
vote
1answer
40 views

Introducing S matrix in scattering theory

What was the need to introduce the concept of S matrix in scattering theory?while we were studying scattering with partial wave analysis.
0
votes
1answer
30 views

Electron count in radioactive decay

I was studying nuclear physics this day and I read about radioactive decays. $\beta$-plus decay turns one proton in the nucleus into one neutron, one positron and one neutrino. I was wondering about ...
0
votes
0answers
26 views

Does nuclear binding energy concern nuclear force or EM force?

From my understanding, binding energy is the energy required to separate all nucleons in a nucleus an infinite distance away from each other. I cannot tell whether this ignored the effect of one of ...
1
vote
0answers
32 views

Interpretation of random matrix eigenvectors in physics

Random matrices may be used in physics to replace Hamiltonian of complex system, for instance in nuclear physics. Eigenvalues of these matrices are simply interpreted as the energy levels (even if we'...
0
votes
0answers
46 views

Is the nuclear force the cause of nucleus surface tension?

At first it looks like an easy question. If we imagine a stright row of three protons and two neutrons connected in the way one neutron comes after one proton how they can spontaneously form a ...
0
votes
3answers
51 views

How can heavier elements be made from hydrogen atoms?

In a JRE podcast from a few years ago, talking about the idea of a universal constructor, Sam Harris said that we could go to a near-vacuum area of deep space, collect nothing but hydrogen atoms, ...
0
votes
1answer
29 views

How to estimate exposure in Roentgens/hr from 99m Tc on a given distance?

I tried to find out how to calc it myself, but seems it's not something very straigthforward... I hope it's not a bad question, sorry if it is! So, this is known: It's 99mTc Let's assume it's point ...
0
votes
0answers
22 views

Could one, with enough electricity to spare, use particle accelerators to mass produce heavy elements

If electrical, and economic limitations are ignored, would it be possible for a civilization to mass produce many millions of tonnes of useful heavy elements using particle accelerators? 1. Could they ...
3
votes
3answers
116 views

Please clarify Uranium-235 critical mass achievement and how much energy is released

I've been watching an MIT course which explains the way that a nuclear bomb works. I am not a physicist or physics student, however; I am a computer scientist. As such, I am not looking for a level of ...
0
votes
2answers
51 views

Is energy mass equivalence ficticious when not at rest?

Here are some examples from my textbook I will refer to, which I could not copy paste, I understand that $E=mc^2$ applies fine for thinking about rest energy, but when the body is not at rest, would ...
0
votes
0answers
7 views

Converging radiation absorbed dose area product to absorbed dose

I would like to do a seeds irradiation experiment. I did read some papers and they all use Gray as unit of measure, however I have never seen seed weights reported. How did they calculate that, ...
0
votes
1answer
37 views

Nuclear force and binding energy

What i read about binding energy is that it is the energy released when nucleus is formed due to the attraction of the strong nuclear force between nucleons. But even after the nucleus is formed, the ...
13
votes
3answers
4k views

If a neutron decays to proton + electron, and a proton can decay into neutron + positron, doesn't this mean neutron = neutron + electron + positron?

I was just watching some videos and came across beta+ radiation (when a positron is emitted). It then occurred to me, how can the following be true, given that a positron and an electron have the same ...
1
vote
1answer
21 views

Probability of a particle travelling a distance before decay

I want to find the probability of a particle travelling a distance greater than 0.5mm before it decays. I know the mean lifetime of the particle at rest and it's momentum components. I know how to ...
0
votes
0answers
32 views

Can deuterium be formed by gamma rays?

I was thinking whether gamma rays could form deuterium by this reaction where gamma rays are really common. $$p^+ +\gamma(1.98\ Mev)\rightarrow n^0 + e^+ + \ \nu_e$$ $$p^+ +n^0\rightarrow d + 2.2\ ...
0
votes
0answers
29 views

Fermi's golden rule, Hamiltonian

I have 1 question about the Fermi's golden rule. The question is: In the introduction of this theory, for explaining the $\beta$ decay, we suppose that the Hamiltonian is of the form: $H=H_0+H_I$ ...
4
votes
2answers
90 views

How do we observe that $\frac{dN}{dt} \propto N$?

I was learning how do derive the radioactive decay formula which starts with the experimental observation that the rate of decay is directly proportional to the amount of isotope present. i.e. $\frac{...
0
votes
1answer
44 views

Thermal neutrons in fission

I read this: These so-called fast neutrons do not cause fission as efficiently as slower-moving ones so they are slowed down in most reactors by the process of moderation. Why slowly neutrons "...
0
votes
1answer
38 views

Does more binding energy between nucleons in different elements as they have more nucleons mean the nuclear force between them is stronger?

My picture of fission is that the nuclear force is the centripetal force and the electrostatic is the centrifugal one and when some energy helps the electrostatic force the nucleus reacts with fission....
0
votes
0answers
14 views

How to find the most probable decay product energy?

Let there be some energy spectrum for some product particle x emitted in a decay: $$\frac {d\Gamma} {dE_x} = f(E_x)$$ where $E_x$ is the energy of particles x. To find the most probably energy for ...
0
votes
1answer
50 views

Where could I find a reliable source that states all the existing radioactive decays?

According to searches on many sources on the web and books, I could merge informations to deduce that the general possible radioactive decay modes are the following: $\alpha$ (proof that this is a ...
0
votes
0answers
14 views

Is the so-called $\gamma$ radioactivity corresponding to the so-called $\gamma$ emission of the isomeric transition?

According to information on radioactivity, for example : https://en.wikipedia.org/wiki/Nuclear_isomer#Decay_processes Isomeric transition is made of two processes : $\gamma$ emission and internal ...
1
vote
2answers
27 views

Beta+ Decay the Mass Missing [closed]

I am confused with such a question: What is energy released in beta+ decay ${^{36}_{20}Ca} \rightarrow {^{36}_{19}K} + {^{0}_{1}e}$ I have a question when I was getting the mass difference. Since ...
0
votes
0answers
11 views

Counting Structure Functions for Mesons

The decomposition of form factors between mesons and baryons can be written as $$ \langle \text{meson}(p') |j^{\mu}(x)| \text{meson}(p)\rangle = \frac{(p'+p)^{\mu}}{2\sqrt{E(p')E(p)}}F(Q^2) $$ $$ \...
0
votes
0answers
17 views

Beta decay and interaction Hamiltonian in nuclei

I just started studying the theory of beta decay and I can't really understand the whole concept of an interaction Hamiltonian. If the nucleons are inside the nucleus the "beta decay" interaction ...
0
votes
1answer
19 views

Why does chart of radiative decay modes appear in two different conventions (x and y axis switched) for english and french versions in wikipedia?

Why does chart of radiative decay modes appear in two different conventions for english and french versions in wikipedia ? Which one is more academic ? On english version, the Z number is in x axis, ...
4
votes
2answers
74 views

Why does the sun have the Fe?

I read the information about 'Abundance in the sun for the elements'. There are a lot of elements in the Sun. I thought 'how is it possible to exist Fe, Au, and so on in the Sun ?', but I couldn't ...
21
votes
4answers
1k views

What happens to alpha particles in matter?

Alpha radiation can be stopped by a piece of paper, but what happens to a helium nucleus after it loses all its energy in matter? Does it became part of the material or does it change nuclear ...
0
votes
1answer
25 views

Electron irradiation of an entire isotope mass

I'm going to post this question in a "goal" and "question" format so it is easier to follow along: The Goal I'm planning on running a nuclear physics experiment in which I have an arbitrary mass of ...
0
votes
1answer
36 views

Solution of diffusion equation for 2 infinite slabs reactor

I have exercise where I have to calculate flux for reactor with 2 same infinite slabs of multiplying medium in vacuum. I have to calculate flux inside slabs and in the slot between them. I am ...
0
votes
1answer
47 views

How much energy is required to fuse two protons? [closed]

What is the kinetic temperature required to fuse two protons in a plasma? How much energy does it release? What are the products of the fusion reaction?
1
vote
1answer
114 views

Derivation of PCAC Condition $\langle 0|J^5_{\mu,a}(x)|\pi_b(p)\rangle=-if_{\pi}\delta_{ab}e^{-ipx}p_{\mu}$?

I have seen the following matrix element quoted millions of times, often called the Partially Conserved Axial Current (PCAC) relation: $$\langle 0|J^5_{\mu,a}(x)|\pi_b(p)\rangle=-if_{\pi}\delta_{ab}e^...
1
vote
0answers
15 views

NuShellX code at around A=132

I have recently started using the NuShellX code to simulate nuclear excited states. I have been able to get the code to work for the exmaples inlcluded such as Ne22 as well as some higher mass nuclei ...
1
vote
1answer
45 views

Solving Bateman equations for decay constants

Given the Bateman equations $$ N_1(t)=N_1(0)e^{-\lambda_1 t} \\ N_2(t)=N_1(0) \frac{\lambda_1}{\lambda_2-\lambda_1} (e^{-\lambda_1 t}-e^{-\lambda_2 t}) $$ And given that the activities $A_1$ and $...
0
votes
1answer
24 views

What is the $^{28}{\rm Si(}d,p)$ nuclear reaction?

I am reading about several processes in nuclear physics that put letters in parentheses next to the names of the isotopes. Usually two letters, separated by a comma. Besides $d$ and $p$, I have ...

1
2 3 4 5
45