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The Bremsstrahlung effect happens when an electron is decelerated by changing its direction typically around a nucleus and then a photon beam is released.

We know that when a scattering happens, let's say Compton scattering, the particle nature of the photon presents itself and the photon hit a free (or valance) electron like a billiard ball then they change courses of motion with different energies and angles.

Now the change in the direction of motion is a change in the direction of the velocity of the electron, which results in the acceleration (or let's say deceleration of a moving electron) of that electron. So this looks like a very quick, sudden and short Bremsstrahlung as in a quick change in motion of an electron when the scattering happens.

If you say that accelerating an electron does not cause an electron to create Bremsstrahlung radiation, you can think this Compton scattering as one of the decelerating types: Incident electron hits a moving electron with a constant velocity and decelerates it or much better changes its direction of motion (acceleration again caused by the change in direction of motion).

Does this cause Bremsstrahlung then because of the same logical assessment?

I mean, is this way of thinking correct? Does Bremsstrahlung happen when any type of scattering happens?

EDIT: Wikipedia : "Broadly speaking, bremsstrahlung or braking radiation is any radiation produced due to the deceleration (negative acceleration) of a charged particle, which includes synchrotron radiation (i.e., photon emission by a relativistic particle), cyclotron radiation (i.e. photon emission by a non-relativistic particle), and the emission of electrons and positrons during beta decay. However, the term is frequently used in the more narrow sense of radiation from electrons (from whatever source) slowing in matter." en.wikipedia.org/wiki/Bremsstrahlung

This link says that acceleration of a charged particle causes Bremsstrahlung radiation also: astro.utu.fi/~cflynn/astroII/l3.html

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  • $\begingroup$ A single electron cannot produce a beam, see the Feynman diagram for brems strahlung here physics.stackexchange.com/questions/249057/… $\endgroup$
    – anna v
    Commented Jun 7, 2023 at 11:24
  • $\begingroup$ @annav Would you explain what you mean by "a single electron" please? My OP does not talk about a single electron. The explanation in the link you provided is not clear to me, and I do not think it answers my OP. $\endgroup$
    – medical physics
    Commented Jun 7, 2023 at 11:27
  • $\begingroup$ This link says that acceleration of a charged particle causes Bremsstrahlung radiation also: astro.utu.fi/~cflynn/astroII/l3.html $\endgroup$
    – medical physics
    Commented Jun 7, 2023 at 12:47
  • $\begingroup$ It is complicated, There is classical electrodynamics where a charged particle is composed of a large number of charges and can give off brems radiation. A single electron has to be treated as the quantum mechanical particle it is, with quantum electrodynamics, which is explained with feynman diagrams and interactions as in the picture in the link I gave. Photons from a great number of electrons add up to the classical brem radiation. $\endgroup$
    – anna v
    Commented Jun 7, 2023 at 12:58

3 Answers 3

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Bremsstrahlung means braking radiation, and involves at least two charged bodies - the body that is braking (e.g. an electron), and the body that causes the braking (e.g. a nucleus, or a group of them).

Various EM radiation scattering scenarios do not have to involve two charged bodies - the radiation would be scattered already by a single charged body (e.g. an electron).

Both bremsstrahlung and EM wave scattering involve at least one accelerated charged body.

EM wave scattering off one charged body is not bremsstrahlung, and does not involve bremsstrahlung.

Bremsstrahlung is not a scattering of an existing radiation, but creation of new radiation.

Accelerated charged particle radiates changes in EM field, and EM field can be ascribed some energy. Changed EM field means changed energy of EM field.

In classical EM theory, scattering of an existing radiation means that electron changes its velocity (in quantum EM theory, electron field changes its state) and produces new (secondary) radiation. Superposition of the primary and secondary radiation is total radiation that can be observed. In the simplified billiard model, the scattered photon is a new photon, and the old photon disappears.

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  • $\begingroup$ Although, I specifically say "Bremsstrahlung", I actually mixed up things. I was actually asking that as we know that accelerated charged particles radiate energy, does scattering itself cause an electron to radiate a new EM wave as it changes its direction or velocity by the hit of an incident photon, thus accelerating? What would you say to that? $\endgroup$
    – medical physics
    Commented Jun 7, 2023 at 13:32
  • $\begingroup$ Wikipedia : "Broadly speaking, bremsstrahlung or braking radiation is any radiation produced due to the deceleration (negative acceleration) of a charged particle, which includes synchrotron radiation (i.e., photon emission by a relativistic particle), cyclotron radiation (i.e. photon emission by a non-relativistic particle), and the emission of electrons and positrons during beta decay. However, the term is frequently used in the more narrow sense of radiation from electrons (from whatever source) slowing in matter." en.wikipedia.org/wiki/Bremsstrahlung $\endgroup$
    – medical physics
    Commented Jun 7, 2023 at 13:46
  • $\begingroup$ I've edited my answer. $\endgroup$
    – Ján Lalinský
    Commented Jun 7, 2023 at 14:28
  • $\begingroup$ Why would old photon disappear? $\endgroup$
    – medical physics
    Commented Jun 7, 2023 at 14:32
  • $\begingroup$ In the billiard view of scattering, one photon comes in, one comes out. If two came out, radiation energy would increase and it would not be called scattering, but emission. $\endgroup$
    – Ján Lalinský
    Commented Jun 7, 2023 at 14:34
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It's all kind of arbitrary. Thomson's classical scattering calculation was based on the acceleration of an electron by electromagnetic waves. Then, in the Compton effect is the outgoing photon the "same" as the incoming one? It's not something that an experiment can decide, so it's not a proper physical question.

Nature doesn't care about how we classify phenomena.

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  • $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Physics Meta, or in Physics Chat. Comments continuing discussion may be removed. $\endgroup$
    – Buzz ♦
    Commented Jun 8, 2023 at 18:16
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There is a lot of misleading and confusing information out there regarding Bremsstrahlung. This is because there really are two definitions - a broad one and a narrow one, and they are all too often conflated. Allow me to elucidate on the broad one.

Bremsstrahlung is created by the acceleration of any charged body. Classically, this can be understood from creating a time-dependence in the electric field emitted by that body. As a time-dependent electric field creates a time-dependent magnetic field, and vice versa, this results in the propogation of radiation emitted from the charge. This happens regardless of the cause of acceleration.

Yes, quantum mechanics provides its own description, but it ultimately results in some spectral variance, not a total change in whether the emission occurs at all (bound states being a special case, that I'm not going to get into).

This means that bremsstrahlung is the result of any interaction that results in an acceleration on a charge. This includes all scattering events, Lorentz force interactions, gravitational interactions, and so on.

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  • $\begingroup$ Scattering of EM wave off a charged particle involves acceleration of this particle and production of secondary emission, but this is not a case of bremsstrahlung. $\endgroup$
    – Ján Lalinský
    Commented Jun 7, 2023 at 21:00
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    $\begingroup$ As I said, there isn't a single consistent definition of bremsstrahlung. By a broader definition of simply being radiative emission caused by the acceleration of a charge, this does qualify. $\endgroup$
    – Logan J. Fisher
    Commented Jun 7, 2023 at 21:04
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    $\begingroup$ There is - braking radiation when matter stops the particles. It is true the term is used for other scenarios as well, such as for cyclotron/synchrotron radiation. But it is almost never used for scattering. $\endgroup$
    – Ján Lalinský
    Commented Jun 7, 2023 at 21:06
  • $\begingroup$ My intent was to give as broad of an answer as possible. Nature doesn't care how we categorize things - all that really matter is the underlying operations resulting in emission. I would certainly not include any sources of radiation that don't strictly depend on the acceleration of a charge. $\endgroup$
    – Logan J. Fisher
    Commented Jun 7, 2023 at 21:09
  • $\begingroup$ Every radiation emission is caused by acceleration of a charge. $\endgroup$
    – Ján Lalinský
    Commented Jun 7, 2023 at 22:28

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