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).

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What makes diffraction spikes move with the focus?

This is a bit of a follow up on The Bahtinov focusing mask and it came with this question on astronomy https://astronomy.stackexchange.com/questions/38443/what-is-it-about-the-layout-of-the-three-...
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How could the collision cross section be a probability?

I am new to learning about the concept about the collision cross section. I am having a hard time understanding the collision cross section (defined as $\sigma_{AB}=\pi(r_A+r_B)^2$ in this link ). But ...
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Is Inelastic Neutron Scattering (INS) any good compared to synchrotron IXS for determining phonon dispersion relations?

Both INS and IXS can be used to study phonon dispersion relations. While INS requires large sample size due to low inelastic scattering cross section, IXS using synchrotron x-ray sources do not ...
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Expansion of relativistic scattering matrix

In the paper I am going through it says that the scattering amplitude $M$ (i assume this is essentially the S-matrix) can be split up into angular momentum components (I assume this means partial wave ...
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Polarization of sunlight by the earth's atmosphere

I have just learned that sunlight traveling through the earth's atmosphere picks up a net polarization by collisions with molecules ($O_2$, $N_2$, etc.) that the photons encounter. One would think ...
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Why is the max. polarization of the blue sky at 90 degrees angle with the sun?

Looking at the blue sky using my polarizing sunglasses I notice an effect (details below), that seems to match well to this answer, where it is said: The greatest degree of polarisation occurs when ...
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Finding the Lagrangian term from a scattering amplitude

I am reading the book Scattering Amplitudes in Gauge Theory and Gravity from Elvang and Huang. In section 2.6 they seem to suggest that the mass-dimension of the kinematic part of the amplitude is in ...
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Singlet to triplet transition in nucleon-nucleon scattering

Is there is might be a Nucleon-Nucleon scattering in which there would be transformation from a state with a total singlet spin state i.e $S=0$ to the one with total spin of triplet represantation, i....
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Scattering of Light by Pure Water

I'm looking for a quantitative (and accessible) description on the scattering of NIR light (850 nm) by pure water. More specifically, I want to find how much of the incident 850 nm light beam is ...
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Is the rate of the reaction $a+b\rightarrow c\rightarrow e+f$ the same as $e+f\rightarrow c\rightarrow a+b$

In particle physics, is the rate of the reaction $a+b\rightarrow c\rightarrow e+f$ the same as the one of $e+f\rightarrow c\rightarrow a+b$ ? If so, then what does prevent that the final states goes ...
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Why is the plane wave ansatz appropriate for scattering cross sections of a localized particle beam?

This question is a spin-off from this related question: Why does the Born approximation for the scattering amplitude depend on the potential $V$ everywhere in space, unlike classical scattering? This ...
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The polarization summation for photons

I was interested to know how we can prove the summation polarization for photons which is $\sum\epsilon_\mu\epsilon^*_\nu\xrightarrow{}-g_{\mu\nu}$ for the process $e^-\gamma\xrightarrow{}e^-\gamma$???...
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Conditional average of a field in physics: $\langle \Psi \rangle_{ij}^i = \langle \Psi \rangle_i^i$

I was just reading this article on the quasicrystalline approximation (QCA). The article abstract says the following: The quasicrystalline approximation (QCA) was first introduced by Lax to break the ...
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Black Hole S-Matrix

I am reading arXiv:2006.03606 where through Eq. (1.1) they say that the transition amplitude for collapse of matter from initial state $\Psi_{i}$ into a black hole and eventually evaporation of black ...
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Is the $S$-matrix a scalar operator?

The scattering $S$ operator which is defined to be the operator corresponding to $S$ matrix should be rotational invariance, does this imply $S$ operator is a scalar operator?
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How to verify my calculated amplitude under gauge invariance structure?

I calculated the Compton amplitude of three diagrams but how can I verify it under gauge invariance structure? $$ {\cal A} = 2 e^2 \left[ \frac{ p_3 \cdot \epsilon_1 p_2 \cdot \epsilon_4^* }{ p_2 \...
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Why does the Born approximation for the scattering amplitude depend on the potential $V$ everywhere in space, unlike classical scattering?

The expression for the first-order Born approximation to the scattering amplitude goes like $$ f(\theta) \propto \int d^3 r e^{-i ( k - k_i)r} V(r) $$ and so in particular the value of $ V(r) $ ...
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Detailed balance: What does one rigourously mean by the transition rate $dw$?

Consider (for example) non-relativistic electron-impact ionisation, in which an effectively stationary atom in state $I$ is struck by an electron of momentum ${p_1}$, producing an atom in state $J$ ...
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Expressing diffraction probabilities as a Fourier sum when solving the atom-surface scattering problem in QM

In the quantum theory of gas-surface scattering, we can expand various functions pertaining to the problem as a Fourier series over the reciprocal lattice vectors. If we define $\mathbf{r}_{S} = x\...
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Reflection and refraction by moving charge: can method of images be used?

Suppose we have a point charge moving inside the halfspace $z>0$ with a given trajectory $r(t)$. Assume that $z>0$ halfspace is Vacuum and the $z<0$ halfspace is glass or some linear ...
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Scattering in pion-proton-neutron theory with isospin conservation

I am following Sidney Coleman's lecture of Quantum Field Theory. In ch 24.3 (starting from page 516) he discussed how to use isospin concept to consider the scattering of one nucleon and one pion. I ...
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Can Rayleigh scattering be thought of as a special case of the Compton scattering?

The presence of the unmodified line (wavelength) in the scattered X-ray beam, in a Compton scattering experiment, is called the Rayleigh line. This line originates from the Compton scattering of the X-...
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What is particle under potential in quantum field theory?

Let's say we solve the Schrodinger equation with infinite well. We can quantize the field by the resonance state and can get the annihilation and creation operator. So we will get the sort of particle ...
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In the generation of X-Rays, why the incoming electron generated from anode knocks out the K shell electron rather than outer shell electrons?

When the high energy beam of particles or photon hits the cathode, electrons from $K$ shell are knocked in the generation of characteristic x-rays. Why do inner electrons get knocked out?
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In/out states in scattering theory, Weinberg vol 1

Chapter 3 of volume 1 of Weinberg's QFT says the following regarding in and out states in scattering theory: Implicit in the definition of the states is a choice of the inertial frame from which the ...
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How can we knock out a proton specially to change one element to another?

I know one can simply excite a nucleon from a nucleus by radiating gamma rays on that nucleus, or knock the nucleus with neutrons or protons. But how can we knock out a proton specially to change one ...
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Pump and Stokes waves in scattering phenomena

what do pump and stokes waves mean? On the web there is a lot about them when we search something about for instance Brillouin and Raman scattering, but I have never found a definition for them. For ...
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Confusion among channel $u$ and channel $t$ in exclusive reactions

In the this paper (https://arxiv.org/abs/1203.4392), on page 2 it is said that Since DVCS amplitude is symmetric under $s \leftrightarrow u$ channel crossing, the CFFs and $^{S}C^i_{\cdots}$ ...
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Scattering in QM/NRQM vs QFT

As discussed in this question: How does a wave packet get scattered? And shown in, for example, this video: https://www.youtube.com/watch?v=iq4lGVznr_8 In quantum mechanics particles are scattered due ...
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Scattering vs Stimulated Emission

I am currently reading Practical Flow Cytometry, fourth edition, by Howard M. Shapiro. The author says the following when discussing scattering: Scattering, which explains both reflection and ...
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What is thephysical meaning of transport cross-section?

Wikipedia explains the momentum transfer cross-section: https://en.wikipedia.org/wiki/Momentum-transfer_cross_section What is its physical meaning? I interpret it as the displacement rate. For ...
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Is the Dirac-Fock electron density model is the most accurate one?

Salvat, F. et al. (2005) reported numerical Dirac-Fock electron density model provides the most accurate description of the electron density model of a nuclear charge. Why? For example why is that ...
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When/where does gamma-gamma scattering occur and what would it look like on a large scale?

I was listening to an interview with Brian Cox and he mentioned that gamma-gamma scattering is when two photons "bounce off" each other and it occurs at "sufficiently high energy." ...
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Electron neutrinos propagating in the Sun dispersion relation $ E \simeq|\boldsymbol{p}| \pm \sqrt{2} G_{F} n_{e} $

Given the following effective lagrangian describing electron neutrinos propagating in the Sun and scattering via charged current processes with a background of non-relativistic electrons $$ \left[i \...
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Proton Scattering by partonic Photon interaction

In my experimental introductory course about Particle-Physics we discussed the deep inelastic scattering of an electron with a proton, where the electron interacts with a parton within the proton by ...
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Dispersion Relation of Quasiparticle in Superfluid

I am now reading a book "Superconductivity, Superfluids, and Condensates" by Jame F. Annett. I am stuck at the part of writing dispersion relation of the quasiparticle in superfluid here. ...
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Scattering amplitude of open + closed strings and D-Branes

When calculating the scattering amplitude of $n$ open string tachyons and $m$ closed string tachyons on the disk, I'd like to understand why choosing the open string tachyons to be attached to $D_{25}$...
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Understanding quantum cross sections as areas

In scattering cross sections we deal with $d\sigma/d\Omega$, incident area per scattered solid angle. When a particle scatters into a small finite $\Delta\Omega$, the incident particle was in a small ...
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Tunneling effect - causes

I'm currently studying QM, and in my class tunneling effect was mentioned, but with no details. I was wondering what exactly causes this effect? Is this due to the wave characteristics of the particle,...
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What is the Critical impact parameter for photons of a black hole?

What is the "Critical impact parameter" for photons of a Black hole with a Radius $r$? Here I'm defing the Critical impact parameter $C$ as the value such that. A photon with an impact ...
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Partial waves method in scattering problems

One way of deal with scattering problems is to use partial wave analysis. This is the procedure I've found in my notes: It's assumed that the observer is in the center-of-mass reference frame and the ...
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Why does the moon sometimes look reddish yellow?

So the question is clear from the title itself. Only sometimes does the moon when it just rises above the horizon, looks reddish in colour. This mostly as I have seen occurs when the moon rises when ...
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Poles of a transmission coefficient

I stumbled on the question I can't quite grasp: What is the meaning of poles for transmission probability $T(E)$? $$ T(E) = \left( 1+\frac{1}{4}\frac{V_0^2}{E (E+V_0)} \sin^2 \left(\frac{2 a}{\hbar }\...
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Schrodinger equation for fermi pseudo potential

This may very well be a very basic question, but I am somewhat confused by a version of the Schrodinger equation I have encountered studying quantum scattering. Let us assume we have some potential ...
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Scattering state solution for delta well

For delta well $V(x) = -a \delta(x)$ we have the solution for TISE as $$\psi_1(x) = A e^{ikx} + B e^{-ikx}$$ for $x<0$ and $$\psi_2(x) = F e^{ikx} + G e^{-ikx}$$ for $x>0$ where $k>0$ after ...
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Scattering vs bound states solution

When we solve Schrodinger equation with potential goes to 0 at large distance, if $E>0 $, the wave function dies away to zero (as this shows). My idea to prove this fact is using curvature, since ...
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Singular Integrals in Scattering Theory [closed]

This might seem a bit off-topic question but it comes into different physical theories. While learning quantum scattering I came across certain singular integrals but could not compute them. I am ...
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Can I ignore the integration function in the amplitude of a scattering process for the scalar Yukawa theory?

When calculating the amplitude of a scattering process for the scalar Yukawa theory involving two scalar ($\phi$) and two complex scalar particles ($\varphi$ and $\bar{\varphi}$) I have noticed the ...
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Photon polarization vectors in Compton scattering by electrons

I was studying the photon polarization sum process (second edition QFT Mandl & Shaw, pages $145$ and $146$) and got stuck in how to get certain equations. We work in a gauge in which the ...
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Calculation of a 2D scattering length with different masses along x and y - contact interaction

I want to calculate the 2D scattering length of two particles with equal (but anisotropic) masses interacting via a pseudo contact potential. In a relative coordinate system, the Schrödinger equation ...

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