5
votes
1answer
70 views

Is there still mystery about spin crisis?

The gluon is a vector boson; like the photon, it has a spin of 1. If this is true and if we know the spin of protons and neutrons then why the news SPIN COMES FROM GLUONS? is telling that, we ...
1
vote
1answer
39 views

Nuclear shell model - finite square well

I am trying to make a simplified approximation and solve Schrodinger equation in the finite square well to model the nucleus of Ca (shell nuclear model). The potential is $ V(r) = -V_0$ for ...
1
vote
0answers
38 views

Subnuclear physics vs wave function

This question is more a philosophical question than a physics one. When we appreciate particle physics we study that in order to explain some experimental results we have to introduce a new particle ...
4
votes
1answer
54 views

Effect of pressure increase on electron orbital wave functions

One of my nuclear physics exercises was to find out if increasing the pressure of a sample of $^{7}\textrm{Be}$ would increase the chance of electron capture to $^{7}\textrm{Li}$ occur. My reasoning ...
1
vote
2answers
87 views

State of constant motion

Why does an object remains in its state of constant motion if there are no forces acting on that object? My understanding is that all the energy of the motion will be kept inside and a change in the ...
2
votes
0answers
81 views

physical intuition behind quasi-bound state formation in feshbach resonance

In Feshbach resonance, by scattering theory formalism it is found that the resonance in cross-section happens when bound state energy of the closed channel is near to the scattering state energy of ...
2
votes
0answers
35 views

how is feshbach resonance potential term physically produced?

In Feshbach resonance model, a 2*2 potential term with space dependent diagonal and non-diagonal terms is written $\left(\begin{array}{cc} V_{11}(\mathbf{r}) & V_{12}(\mathbf{r})\\ ...
2
votes
1answer
85 views

Angular momenta of photon

$A^\mu$ can have multipole expansions in classical electrodynamics. This gives rise to dipole photon, quadrupole photon etc. For dipole photon $j=1$ (In electrodynamics books they write it as $l=1$). ...
1
vote
1answer
84 views

Coupling of open and closed channels in Feshbach resonance model

Feshbach resonance is described with coupling of 2 systems differing in the form of potentials :- one is said to produce a bound state (in 'closed' channel) and other is to produce scattering states ...
1
vote
2answers
76 views

What causes different decays?

Nuclei spontaneously decay according to a certain decay rate. There are however different kinds of decay, alpha, beta, gamma... What causes then the nuclei, when they decay, to do so in one way of ...
1
vote
0answers
28 views

Troubles with the Nucleon Bound Energies

I was reading my quantum mechanics text and I have a doubt. I have the energy levels well defined for the finite square well and the author suddenly compares (I believe) those levels with the levels ...
3
votes
0answers
94 views

Geometric quantization AND nuclear physics

Classical mechanics has a natural mathematical setting in symplectic geometry and it may be asked if the same is true for quantum mechanics. Geometric quantization is one formalization of the notion ...
3
votes
1answer
296 views

Nuclear Spin of Sodium 23

I am actually calculating the nuclear spin of Sodium 23. Here we have 11 protons and 12 neutrons. Now both the nuclei are short of the magic numbers. When I use the shell model for protons and ...
1
vote
1answer
860 views

What prevents an atom's electrons from “collapsing” onto its protons? [duplicate]

Forgive me if the answer to this is obvious. I have no formal physics training, and I remember that when I asked my physics teacher this, she just frowned and said "Good question." An electron is ...
4
votes
0answers
106 views

Is there a difference between “two photon absorption” and “double quantum transitions”?

Wikipedia has articles on two photon absorption. And a lot of NMR literature refers to double quantum transitions. But is there a difference? As far as I can tell, a double quantum transition is has ...
3
votes
2answers
218 views

Proton-proton bound state

There is something unclear for me. We say that the deuterium is a proton-neutron bound state of orbital angular momentum L=0 and of total spin S=1. I don't understand why can't we build such a state ...
1
vote
1answer
81 views

Wave Function of Particle in Nuclear Reaction

I was thinking and came up with the question of what happens to the wave function of a particle that decays into energy, say a neutron in a nuclear reaction. I know that conservation of probability ...
10
votes
1answer
643 views

With what probability does nuclear fusion occur at energies far below the Coulomb barrier?

Even at the core of the sun, the temperature of $\sim 10^7$ K only results in $kT\sim1$ keV, which is about a thousand times less than the electrical potential energy of $\sim1$ MeV needed in order to ...
0
votes
0answers
29 views

Computing the Ideal Rotational Ratio of B(E2;2+ to 0)/[Q(2)]^2

Although the title is fairly specific, I was wondering how the following is computed by assuming ideal collective nuclear rotation: $$ \frac{B(E2;2^+_1 \to 0^+_1)}{[Q(2^+)]^2}\approx .244 $$ I'm, ...
-1
votes
1answer
86 views

Nillson Potential [closed]

We define a Hamiltonian to derive Nilsson potential, $$\hat{H}=-\frac{\mathbf{\hat{p}}^2}{2m}+ \frac{1}{2}m\left[\omega_\bot^2(\hat{x}^2+\hat{y}^2)+\omega_z^2\hat{z}^2\right]$$ Nilsson model is a ...
0
votes
1answer
262 views

Coordinate system

Quoting from 'Nuclear Physics - Theory and Experiment' by RR Roy, BP Nigam 2005 edition Link to text How did the author arrive at equations (23a, 23b,23c)? Chapter 8 Nuclear model II, 8.7 ...
0
votes
1answer
107 views

Rotational Hamiltonian for collective model

The effect of rotation can be considered by modelling the nucleus as a rotating body, characterised by some moment of inertia. Then how The Hamiltonian describing rotation is? ...
0
votes
0answers
70 views

Symmetry for even even nuclei

For even even axially symmetric nuclei K=0 because even even spherical nuclei don't show rotaional spectra and therefore do not rotate about the axis of symmetry; Thus the angular momentum about a ...
1
vote
0answers
158 views

Hamiltonian Nuclear collective model

Let $\mathscr{I}_3$ and $\mathscr{I}$ are the moments of inertia for rotations about symmetry axis 3 and about an axis perpendicular to it , and I is the angular momentum operator with components ...
2
votes
1answer
106 views

One body harmonic oscillator states expressed in terms of creation operators

I am reading trough chapter one of Moshinsky's "The harmonic Oscillator in Modern Physics". However i am having some trouble with the mathematics in section 8 of chapter 1. I will sketch a summary of ...
2
votes
1answer
106 views

Uncertainty Principle on System of particles

I am new to Quantum Mechanics. I read the uncertainty principle - it says there are pairs of physical quantities which can't both be determined with certainty for a particle. My question is does the ...
1
vote
1answer
302 views

what is the magnetic quadrupole operator?

To find magnetic or electrical moments in quantum theory we must calculate the expectation value of an appropriate operator. the dipoles operator are similar and is easy to find but the magnetic ...
0
votes
0answers
293 views

What is the magnetic quadrupole moment of a nucleus in cylindrical coordinates?

What is the magnetic quadruple moment of a nuclei in cylindrical coordinates? The quadrupole moment of a nucleus is zero in spherical coordinates but in the cylindrical coordinates it can't be ...
3
votes
1answer
278 views

Why is the total interaction cross section larger for incident particles with lower energy?

The cross section of a nuclear interaction is a measurement of the probability of that interaction occuring. These probabilities are typically presented in terms of barns ($10^{-28}$ m$^2$) as a ...
4
votes
2answers
246 views

nuclear fission and half life

Why is the alpha, beta or gamma decay of an unstable nucleus unaffected by the chemical situation of an atom, such as the nature of the molecule or solid in which it is bound? The chemical situation ...
6
votes
0answers
114 views

Can we excite a nucleus by means of very intense low energy gamma-photon irradiation?

The phenomenon of multi-photon ionization of atoms has been studied, both theoretically and experimentally, for several decades. Intense laser beam devices are the apparatuses used for the ...
4
votes
5answers
1k views

How can the nucleus of an atom be in an excited state?

An example of the nucleus of an atom being in an excited state is the Hoyle State, which was a theory devised by the Astronomer Fred Hoyle to help describe the vast quantities of carbon-12 present in ...
4
votes
1answer
209 views

Why is the Wick contraction in HFB or BCS equal to a single-particle density?

I'm trying to understand how in Hartree-Fock-Bogoliubov (HFB) or BCS theory we can write a product of creation/annihilation operators as single-particle densities under the guise of "Wick's theorem". ...
0
votes
1answer
84 views

Optimal methods for mapping out molecules, atoms and nuclei and their energy levels?

I'm wondering if it would be possible to map out all the different types of molecules, atoms and nuclei and their energy levels on one page (even if in a generalised way)? But perhaps I'm referring to ...
1
vote
1answer
193 views

About Efimov States and Halo-Nuclei

I read that Halo nuclei could be seen as special Efimov states, depending on the subtle definitions. (The last sentence in the second to last paragraph of this Wikipedia article.) This does ...
-1
votes
1answer
161 views

Direct nuclear reactions problems [closed]

can anyone explain Multi-step nuclear reactions in terms of direct nuclear reactions .
0
votes
1answer
199 views

Direct nuclear reaction in nuclear physics

Time taken to occur a direct nuclear reaction is very low $10^{-22}$sec . I want to know the Importance of direct nuclear reactions.
5
votes
0answers
961 views

Nuclear/quantum physics simulation software

Is there any software which is able to simulate D-T interaction for example and get temperature-crosssection curve without referencing to any experimental data? Do we have quantum-level simulation ...
1
vote
2answers
349 views

Where does the “borrowed energy” come from in Alpha decay?

I was also thinking about the uncertainty principle in regards with energy & time. The question of something like: Alpha tunneling out of the nucleus is where this can be invoked, but having an ...
4
votes
3answers
167 views

How do we know that internal conversion creates no intermediate photon?

I've read, from several sources, that in internal conversion -- an excited electron transferring its energy to another electron which is then emitted -- no intermediate gamma radiation is produced. ...
4
votes
1answer
751 views

Relationship between nuclear spin and nuclear magnetic moment?

We know that nuclear magnetic moment can be expressed in terms of the expected value for nuclear spin as: $$\langle\mu\rangle =[g_lj+(g_s-g_l)\langle s_z\rangle]\frac{\mu_N}{\hbar}$$ (Cf. Krane), ...
13
votes
1answer
516 views

How come random matrices can predict energy spectra of heavy atoms?

Some of the applications of random matrices is to find the spectra of heavy atoms in nuclear physics which are usually difficult to find otherwise. How can starting from randomness of some kind, ...
6
votes
2answers
1k views

Tunneling of alpha particles

Consider this explanation of the alpha decay: It says The Coulomb barrier faced by an alpha particle with this energy is about 26 MeV, so by classical physics it cannot escape at all. ...
3
votes
0answers
2k views

Energy Levels of 3D Isotropic Harmonic Oscillator (Nuclear Shell Model)

One simple way of detailing the very basic structure of the nuclear shell model involves placing the nucleons in a 3D isotropic oscillator. It's easy to show that the energy eigenvalues are $E = ...
18
votes
3answers
10k views

Why do electrons occupy the space around nuclei, and not collide with them?

We all learn in grade school that electrons are negatively-charged particles that inhabit the space around the nucleus of an atom, that protons are positively-charged and are embedded within the ...
6
votes
3answers
296 views

References on the non-compositeness of the known elementary particles

What paper(s) or theory(s) describe or prove that the elementary particles that we have determined today cannot be made up of smaller more fundamental particles?
10
votes
1answer
528 views

Long time deviations from exponential decay in radioactivity

Are there any examples of common substances whose decay is not exponential? We're used to thinking about radioactivity in terms of half-lives. This is a concept that makes sense only for a decay that ...
3
votes
1answer
1k views

Why must the deuteron wavefunction be antisymmetric?

Wikipedia article on deuterium says this: The deuteron wavefunction must be antisymmetric if the isospin representation is used (since a proton and a neutron are not identical particles, ...
4
votes
1answer
745 views

Fermi's Golden Rule

It is well known that to calculate the probability of transition in the scattering processes, as a first approximation, we use the Fermi golden rule. This rule is obtained considering the initial ...