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, ...

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Light scattering vs roughness

I've been searching for an answer to this question in professional circles for a while; now I'd like to ask here, to find out why the answer is not there :) In my optical modelling (computer ...
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1answer
196 views

Quantum field theory meson scattering calculation (scalar yukawa theory)

Please see this question for a clear background of the notation I use. My issue is that I want to use Wick's theorem to calculate the amplitude of meson ...
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50 views

Color of sky scattering by sky dust [duplicate]

Why does we see sky like blue in maximum time? We know violet has less wavelength, so we should see sky like violet. My assumption is that, violet is not primary color and not sufficient in the ...
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225 views

Setting of renormalization scale in field theory calculations

In dimensional regularization an arbitrary mass parameter $\mu$ must be introduced in going to $4-\epsilon$ dimensions. I am trying to understand to what extent this parameter can be eliminated from ...
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158 views

Rutherford Scattering Spectra

I am using SimNRA to simulate the classical Rutherford Scattering. Playing around with it, I came across some spectra that I cannot explain... First of all, if someone plots the spectrum of ...
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33 views

Impact parameter in scattering process

Let's consider classical two body scattering process. Is the impact parameter the same in the laboratory and inertial frame of references?
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194 views

Concerning Scattering Intensity and Particle Concentration

I am trying to determine what governs my sensor output. I have an optical sensor that emits infrared radiation on a sample volume and gives me a voltage output from the scattering of (1 to 10 micron) ...
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1answer
397 views

Elementary question on pion-proton scattering cross-section

Is $E_k$ the energy of the outgoing or incoming pion? The first peak is supposed to be a delta baryon. What does the graph tell us, experimentally? A pion of kinetic energy x comes in, then we ...
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157 views

Significance of Poles of Correlation Function in QFT

In QFT, specifically in scattering processes, what is the physical significance of the poles / residues of the $N$-point correlation function? And why?
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46 views

Must neutron speed and diffusion speed be comparable for neutron scattering experiments to be probe atomic diffusion?

Neutron scattering experiments are sometimes used to study atomic diffusion in solid materials. My intuition is that the typical speeds of the atoms diffusing in the material--say, the diffusion ...
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332 views

A question from Weinberg QFT

I'm self-studying Weinberg QFT. I'm confused by his treatment of scattering theory . I have the following question: He introduces the free particle states $\Phi_{\alpha}$ but I'm not sure what is ...
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1answer
246 views

Mie scattering intensity and spherical particles on

I am running an experiment where I shine infrared light on (almost) spherical particles on the micron scale (PM2.5 - PM10). I then look at the (90 deg) scattering properties to try and size the ...
7
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1answer
156 views

Do small-angle coherent scattering experiments really see coherent effects over arbitrarily large distances?

Short version After integrating over all possible outgoing angles, the total cross-section of coherent elastic scattering from a fixed target of characteristic length $L$ scales like $L^4$. Does ...
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1answer
100 views

Tunneling and transmission

Lets say we have a tunelling problem in the picture, where $W_p$ is a finite potential step: If particle is comming from the left a general solutions to the Schrödinger equations for sepparate ...
4
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119 views

Neutron scattering for a critical magnetic-ordering system : what about critical opalescence?

Liquid-gas transition critical point is believed to share the same universality class as the 3D Ising model. We know that the liquid-gas transition is characterized by a phenomenon called critical ...
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1answer
348 views

Single photon's effect on conservation of momentum?

When your looking at basic Compton theory you find that if you shoot a stream of photons at a particle (usually atoms or electrons), then you have the basic laws of conservation of momentum. The ...
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2answers
247 views

Attenuation mass-thickness for sunset light

We are able to look directly at the sun near sunset and sunrise, which clearly demonstrates the fact that our atmosphere attenuates visible light. Let's imagine it follows the typical attenuation ...
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114 views

Parton Distribution Functions, average cross section of the nucleon

Say we are given the scattering cross section for neutrinos from $d$ and $\bar{u}$ quarks as $\frac{d\sigma^{d}}{dQ^2}=\frac{G_F^2}{\pi}$, $\frac{d\sigma^{\bar{u}}}{dQ^2}=\frac{G_F^2}{\pi} (1-y)^2$, ...
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34 views

How to write down the detailed balance (microreversed) amplitude

I know that time-reversal of a reaction and the detailed balance (microreversed, or reciprocal) reaction are different. Textbooks on scattering theory explain how to relate the S-matrix elements of a ...
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1answer
377 views

Potential step and its transmission / reflection

Lets say we have a potential step with regions 1 with zero potential $W_p\!=\!0$ (this is a free particle) and region 2 with potential $W_p$. Wave functions in this case are: \begin{align} ...
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1answer
73 views

Do particles in the solar core travel at the same speed as they would in vacuum?

I just read the Wikipedia article on the Sun. The section on Solar Core states It has a density of up to 150 g/cm3[47][48] (about 150 times the density of water) Do the particles (atomic, and ...
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156 views

Wave equations for two intervals at Potential step

Lets say we have a potential step as in the picture: In the region I there is a free particle with a wavefunction $\psi_I$ while in the region II the wave function will be $\psi_{II}$. Let me ...
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2answers
118 views

Why is the energy spectrum continuous for a plane wave when it has energy less than the potential barrier?

Please explain it in the context of this task: we have a potential barrier that looks like $\prod$, with $E<U$. There are 3 regions: 1) no field 2) barrier 3) no field Solution could be ...
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0answers
142 views

Are EM waves scattered the most when the wavelength and the obstacle have a similar size?

I heard that when the wavelength and obstacle are similar in size, the scattering is the greatest. Is this true?
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1answer
214 views

Alternative methods to derive the static potential in the NR limit of QED

In QED, one can relate the two-particle scattering amplitude to a static potential in the non-relativistic limit using the Born approximation. E.g. in Peskin and Schroeder pg. 125, the tree-level ...
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162 views

Classical scattering of two particles by a Yukawa potential

A point-like particle $A$, coming from minus spatial infinity, heads at another one, $B$, with an impact parameter of $b$. Initial momenta are $p_A$ and $p_B=0$. They repel each other via a Yukawa ...
4
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1answer
307 views

Why does scattering depend on spin?

I'm reading about giant magnetoresistance (GMR), and the most important feature of this phenomenon is the spin dependance of the electron scattering inside a magnetised lattice. However, I don't quite ...
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246 views

Database of scattering amplitudes

I want to check whether my result for the invariant amplitude of the electron-electron scattering (to lowest order in $\alpha$; t+u channels) is correct or not. I can't find any reference that has ...
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312 views

Expansion in solid spherical harmonics on the lattice

I'm interested in calculating scattering processes (e.g. Coulomb scattering of an electron beam by a single ion) in the context of lattice quantum field theory, and wonder if there is something like ...
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2answers
483 views

Optical theorem and conservation of particle current

The optical theorem $$ \sigma_{tot} = \frac{4\pi}{k} \text{Im}(f(0)) $$ links the total cross section with the imaginary part of the scattering amplitude. My lecture notes say that this is a ...
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1answer
86 views

In the expansion of the scattered wave function, why do these two functions have the same index?

See Griffiths Quantum Mechanics, eq. 11.21. Evidently, $$\psi(r,\theta,\phi)=Ae^{ikz}+A\sum\limits_{l,m}^{\infty}C_{l,m}h_{l}(kr)Y_{l}^{m}(\theta,\phi).$$ But I don't see why the $l$th Hankel function ...
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3answers
570 views

Particle coming across a step potential barrier

My quantum mechanics textbook says that when a particle (in the classical case) comes across a potential-step barrier of finite height, if it has sufficient energy to surmount the barrier, it will ...
2
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2answers
167 views

Is there an upper limit to wavelength and particle size in the Mie Scattering solution?

I figure that Mie scattering is best for finding the scattering when the wavelengths are between 1/10th to 10x the particle diameter. However, is there an upper limit to this? If I send 2.8cm ...
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28 views

Phase functions non-existent in original (J. Strutt) Lord Rayleigh's work?

This is related to my previous Phys.SE question on the derivation of the phase function - upon sifting and scanning through 600 pages of John Strutt's collected work, there is absolutely no mention of ...
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473 views

How did Lord Rayleigh derive/determine the phase function for his scattering model?

I've been researching the question for quite some time, as I understand it the phase function is actually an approximation due to the particle-wave duality inherent in participating media such as the ...
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1answer
224 views

Why can I add the Atomic form factors in the calculation of the Diamond Structure factor

When trying to calculate the structur factor for diamond I came across the calculation on the wikipedia. In the calculation they just add up the atomic form factors of alle the atoms in the unit cell ...
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1answer
246 views

Specific electron energy gap values $E_{i+1}-E_i$ vs. photons with arbitrary energy $\hbar \omega$

The energy levels of electrons in an atom are quantized $E_i$. A photon of a specific momentum $\vec p$ and energy $$\omega=(E_{i+1}-E_i)/\hbar$$ hits an atom and gets absorbed. Okay now say the ...
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719 views

What is the capture cross-section of a black hole region for ultra-relativistic particles?

What is the capture cross-section of a black hole region for ultra-relativistic particles? I have read that it is $$\sigma ~=~ \frac{27}{4}\pi R^{2}_{s}$$ for a Schwarzschild BH in the geometric ...
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1answer
141 views

Scattering from a box potential of width $L$ doesn't reproduce a step potential in the limit $L \rightarrow \infty$

Consider the scattering of a quantum particle in one dimension, caused by a step in the potential (this appears in many undergrad level QM books): $$ V(x) = \begin{cases} V_1 & x<0 \\ V_2 ...
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1answer
41 views

What is pulsed neutron diffraction?

I have tried a google search and checked my condensed matter books but I can't find out what pulsed neutron diffraction is and how it differs from inelastic neutron scattering.
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359 views

Can scattering amplitudes be simplified with 1PI diagrams?

I have been teaching myself quantum field theory, and need a little help connecting different pieces together. Specifically, I'm rather unsure how to tie in renormalization, functional methods, and ...
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1answer
255 views

Integral in Peskin and Schroeder

I'm having a bit of a slow day, and can't see how to do the following integral in Peskin and Schroeder (page 107 for anyone with the book). We've derived in the centre of mass frame the integral over ...
4
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1answer
459 views

Scattering Processes in Scalar Yukawa Theory

I'm trying to compute nucleon-nucleon scattering in scalar Yukawa theory. Here we view a nucleon as a complex scalar field $\psi$ and a meson as a real scalar field $\phi$. They interact through ...
3
votes
1answer
160 views

Inclusion of information about external particles to calculate scattering amplitudes

In this (schematic) equation to calculate the scattering amplitude A by integrating over all possible world sheets and lifetimes of the bound states $$ A = \int\limits_{\rm{life time}} d\tau ...
2
votes
2answers
391 views

How does scattering work?

Why is the sky blue? I was always taught in high school that light with wavelength $\lambda$ acts like a little particle that wiggles up and down through space (in proportion to its magnitude). I was ...
2
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1answer
581 views

Feynman Rules for massive vector boson interactions

I am stuck at the beginning of a problem where I am given an interaction term that modifies the regular QED Lagrangian. It involves the interaction between a photon field and a massive vector boson: ...
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1answer
161 views

Scattering Amplitudes in Centre of Mass Frame

I'm reviewing page 59 of the QFT notes here and am a little confused by a reference frame argument. You can compute the second order probability amplitude term for nucleon-nucleon scattering to be ...
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3answers
1k views

Why is the colour of sunlight yellow?

I was going through the preliminary papers of other schools and found a question that I did not know. It was "Why sunlight appears yellow?". Can anyone answer it?
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22 views

Hamiltonian of the charged current in SM (related to the lorentz invariance)

recently when I was studying the scatterings which involves a vector boson (like W boson) as an intermediate particle, I saw that the propagator is not Lorentz invariant, I read that there is another ...
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2answers
358 views

Blue-shifting as opposed to violet-shifting

A recent XKCD comic implies that the sky is blue as opposed to violet due to human physiology, and that animals more sensitive to shorter wavelengths will perceive the Earth's sky as the shortest ...