All Questions
15
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How does a photon interact with EM field of a nucleus thus exchange momentum and recoil the nucleus when pair production happens? [duplicate]
The photon must be near a nucleus in order to satisfy conservation of momentum, as an electron–positron pair produced in free space cannot satisfy conservation of both energy and momentum.[4] Because ...
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1
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Does a moving atom with a nuclear magnetic moment generate an electric field?
I have read that moving ions generate a magnetic field as it moves.
Similarly, is this also true regarding the nuclear magnetic moments of the atom? In other words, would a moving atom with a nuclear ...
- 293
2
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1
answer
113
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Are electric force and strong force equal in magnitude?
Should the electric force and the strong force be equal for a nuclei to be stable? Because if perhaps, the strong force is now more than that of the electric force, then shouldn't the nucleus collapse ...
- 21
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Why were sparks created in Rutherford's alpha particle scattering experiment?
So I just read that when alpha particle hit the gold foil sparks were created. And these flashes were used to determine the angle of scattering. So were the sparks created because the alpha particles (...
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Would atoms be smaller or larger if the electromagnetic force was slightly weaker?
Some sites claim that atoms would be larger in size if the EM force was weaker, because the electrons would 'orbit', on average, farther from the nucleus....
Other physicists claim that atoms would, ...
- 4,509
2
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1
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147
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What is the emission spectra of electrons under the Zeeman/Stark effect?
As the Zeeman effect/Stark effect lead to a change in the energy levels of orbital electrons in relation to their spin, similar to hyperfine transitions, I was wondering what the emission spectra of ...
- 477
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2
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2k
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Can a nucleus (made of neutrons) exist without an EM field?
I understand that the EM field has an EM charge and that a nucleus made of neutrons and protons has an opposite EM charge, and this attracts.
And because the electron's kinetic energy (that would ...
- 29k
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78
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NMR Concept Help
I am trying to grasp the concept of Nuclear Magnetic Resonance machines that use permanent magnets. From what I understand you use a electromagnet to align the atoms with the field, turn off the field ...
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109
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Diffusion of magnetization (NMR)
In the context of MRI I'm trying to understand the mechanisms of magnetization diffusion.
Consider a sample that is magnetized by an external magnetic field. We have displacement of magnetic moment ...
- 191
15
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2
answers
3k
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Why do spin-$\frac{1}{2}$ nuclei have zero electric quadrupole moment?
Why do spin-$\frac{1}{2}$ nuclei have zero electric quadrupole moment? How does this come about, and how can one tell in general whether a spin-$j$ nucleus can have a nonzero quadrupole (or higher ...
- 3,701
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7
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4k
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Why can't electrons fall into the nucleus? [duplicate]
I read a book on pop sci book on quantum mechanics and the author said that electrons do not fall into the nucleus due to quantum mechanics- which principles suggest this (I think it was Heisenberg's ...
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1
answer
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Why are atomic quadrupole moments calculated using nuclear spin?
It's my understanding that electric quadrupoles interact with the gradient of an electric field, and I understand roughly how this works. I am trying to calculate the interaction between an atomic ...
- 373
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3
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5k
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What causes radioactivity? Is it a quantum mechanical effect?
I'm just curious what causes radioactivity. I've been told that in the case of alpha decay, since the nucleus is quantum mechanical, there is a probability that the configuration of protons and ...
- 229
2
votes
1
answer
231
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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 $l=1$). ...
- 26.8k
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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 ...
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