Questions tagged [scattering]

Scattering is a general term for several physical processes in which radiation of some sort changes direction due to an interaction with a particle. Scattering can be classified by the type of radiation (ie, electromagnetic, x-ray, neutron), or by the relative sizes of the wave and the particle (ie, Rayleigh, Mie, geometric).

Basically scattering phenomena, an essential tool in our understanding of microscopic physics - the physics of molecules, atoms, nuclei and elementary particles, refer to interactions between two classes of objects, such as molecules, atoms, electrons, photons and other particles.

  • For example: cosmic ray scattering in the Earth's upper atmosphere; particle collisions inside particle accelerators; electron scattering by gas atoms in fluorescent lamps; and neutron scattering inside nuclear reactors.
  • If the interaction potential between two types of objects is not precisely known, a scattering experiment gives us the opportunity to extract information about the interaction potential.
  • Depending on the state of the final-state particles scattering phenomena can be conveniently classified into the following processes.
    $(a)~$ Elastic scattering $~~~(b)~$ Inelastic scattering $~~~(c)~$ Rearrangement or breakup or reaction
  • Scattering theory is a framework for studying and understanding the scattering of waves and particles.
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Scattering of light by light: experimental status

Scattering of light by light does not occur in the solutions of Maxwell's equations (since they are linear and EM waves obey superposition), but it is a prediction of QED (the most significant Feynman diagrams have a closed loop of four electron…
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Why can we treat quantum scattering problems as time-independent?

From what I remember in my undergraduate quantum mechanics class, we treated scattering of non-relativistic particles from a static potential like this: Solve the time-independent Schrodinger equation to find the energy eigenstates. There will be…
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Why does the sky change color? Why is the sky blue during the day, red during sunrise/set and black during the night?

Why does the sky change color? Why is the sky blue during the day, red during sunrise/set and black during the night?
user68
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Phase shifts in scattering theory

I have been studying scattering theory in Sakurai's quantum mechanics. The phase shift in scattering theory has been a major conceptual and computational stumbling block for me. How (if at all) does the phase shift relate to the scattering…
Cogitator
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Why can't we see gases?

I am not sure what causes gas molecules to be invisible.This question may look silly but I really want to know the story behind it.
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Scattering, Perturbation and asymptotic states in LSZ reduction formula

I was following Schwarz's book on quantum field theory. There he defines the asymptotic momentum eigenstates $|i\rangle\equiv |k_1 k_2\rangle$ and $|f\rangle\equiv |k_3 k_4\rangle$ in the S-matrix element $\langle f|S|i\rangle$ as the eigenstates of…
SRS
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Why does the moon sometimes appear giant and a orange red color near the horizon?

I've read various ideas about why the moon looks larger on the horizon. The most reasonable one in my opinion is that it is due to how our brain calculates (perceives) distance, with objects high above the horizon being generally further away than…
logicbird
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Why aren't rainbows blurred-out into nothing after they are produced?

I understand how a prism works and how a single raindrop can scatter white light into a rainbow, but it seems to me that in normal atmospheric conditions, we should not be able to see rainbows. When multiple raindrops are side-by-side, their…
spraff
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Use my example to explain why loop diagram will not occur in classical equation of motion?

We always say that tree levels are classical but loop diagrams are quantum. Let's talk about a concrete example: $$\mathcal{L}=\partial_a \phi\partial^a \phi-\frac{g}{4}\phi^4+\phi J$$ where $J$ is source. The equation of motion is $$\Box \phi=-g…
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How did Rutherford conclude that most of the mass (as well as the positive charge) was concentrated in the nucleus?

Geiger and Marsden's experiment led Rutherford to believe that the positive charge and most of the mass of the atom was concentrated in a small region. I understand what led him to conclude the way the positive charge is positioned in the atom. But…
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Systematic way to draw all inequivalent Feynman diagrams

I am wondering whether there is some systematical approach to find Feynman diagrams for S-matrix (or to be more precise for $S-1$ since I am interested in scattering amplitude). For example in $\phi^3$ theory and its variations (e.g. $\phi^2\Phi$)…
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Is the converse of Weinberg's statement on the cluster decomposition principle true?

In Weinberg's "The Quantum Theory of Fields, Vol. 1", Section 4.4, page 182, the author says: We now ask, what sort of Hamiltonian will yield an $S$-matrix that satisfies the cluster decomposition principle? It is here that the formalism of…
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In a vacuum, can you see light which is not travelling towards you?

In air, when there is light propagating in a direction, we can still see it even when it is not primarily travelling in our direction, because a small part of the light hits the air molecules, and changes its direction; it travels towards us. Does…
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'Quantum' vs 'Classical' effects in Quantum Field Theory

After reading a few textbooks on Quantum Field Theory there's something that's always struck me as bizarre. Take a scattering process in QED like $\gamma$,e$^-$ $\rightarrow$ $\gamma$,e$^-$. The leading order contribution to this process starts at…
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As there is no specific boundary of an atom, how was Rutherford able to estimate the size of an atom?

On the basis of the observations, Rutherford drew the following conclusions regarding the structure of an atom: Most of the space in the atom is empty as most of the alpha particles passed through the foil undeflected. A few positively charged…
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