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I'm not a physicist in any way, but I'm curious enough to watch and attend some pop-science lectures.

Let's imagine the following situation - there is a free-standing unbound electron. It has its wave-function describes probabilities to find it in particular position. Also there is incoming photon with a proper wave-length to be absorbed.

  1. How the electron "decides" to absorb it, from what distance? If it's probabilistic too then electrons can absorb photons from centimeters away? And we shoud be able to verify it statistically by observations of many photons and electrons.

  2. Since the photons are stretched out by cosmological expansion, then I assume that they have the length in physical space. Is the absorption instant or does it take time to absorb the "whole" photon?

  3. If the absorption is not instant then it's possible to make a trick: make the electron annihilate with positron - after it started to absorb photon, but right before it finished. What will happen to "unabsorbed part" of photon?

What is a correct theoretical answer to my questions?

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    $\begingroup$ the electron decides to consume it Electrons don’t have consciousness and thus can’t decide to do anything. $\endgroup$
    – Ghoster
    Commented Jul 31, 2023 at 17:29
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    $\begingroup$ @Ghoster by "decides" I mean "some physical process going between electron and photon that leads to the consumption of the later". I thought it's obvious - added quotes for clarity. $\endgroup$
    – abyss.7
    Commented Jul 31, 2023 at 17:32

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a free-standing unbound electron. It has it's wave-function describes probabilities to find it in particular position. Also there is incoming photon with a proper wave-length to be consumed.

This scenario does not exist as described. Free electrons can scatter a photon, but they cannot absorb it.

How the electron "decides" to consume it, from what distance?

It does not absorb it from any distance.

Is the consumption instant or does it take time to consume the "whole" photon?

It does not happen over any period of time.

What will happen to "unconsumed part" of photon?

There is no part of a photon. The entire photon is unabsorbed.

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  • $\begingroup$ Doesn't "scatter" mean "absorb and emit again"? If I'm wrong about free-standing electron, then what about electron inside atom? $\endgroup$
    – abyss.7
    Commented Jul 31, 2023 at 17:46
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    $\begingroup$ It isn’t the electron inside the atom that absorbs the photon. It is the atom that absorbs the photon. The issue is mass. An electron cannot change its mass so it cannot absorb a photon. An atom can. An excited atom is more massive than a ground state atom. That is necessary for absorbing a photon $\endgroup$
    – Dale
    Commented Jul 31, 2023 at 17:51
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    $\begingroup$ I voted to close because your question depends on your own model of what an electron and a photon are, which is not mainstream physics $\endgroup$
    – anna v
    Commented Jul 31, 2023 at 19:12
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    $\begingroup$ @annav how are electrons and photons a personal model and not mainstream physics? They literally are on the usual list of particles in the standard model. The standard model is certainly mainstream physics. Also, shouldn’t this be a comment to the question rather than a comment to my answer? I don’t agree with the closure here $\endgroup$
    – Dale
    Commented Aug 1, 2023 at 11:43
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    $\begingroup$ sorry, should have been on the OP . The words he/she is using are standard model words but the behavior he/she is trying to model with words is not main stream physics, imo $\endgroup$
    – anna v
    Commented Aug 1, 2023 at 19:50
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a free-standing unbound electron. It has it's wave-function describes probabilities to find it in particular position. Also there is incoming photon with a proper wave-length to be consumed.

Free electrons can scatter a photon, which accelerates the electron. The re-emitted photon has a different wavelength. If the electron moves faster than before the temporary absorption, the photon loses energy and its wavelength becomes longer and vice versa.

How the electron "decides" to consume it, from what distance?

There is a radius of action between the electron and the photon. Either they pass each other without influencing each other, or absorption and re-emission occur within the effective radius. Something in between is not known to me (but I would like to know more about it if there are models in physics), because photons are indivisible elementary particles between their emission and their absorption. This is exactly the reason for the simplified statement that free electrons do not absorb photons. But since I can accelerate an electron very effectively with a laser, energy is transferred from the photons of the beam to the electron and inevitably the photons that hit it have a longer wavelength after absorption and re-emission.

Is the consumption instant or does it take time to consume the "whole" photon?

Every process takes time. If we know the radius of action and assume c as the velocity, we would have an indication of half the action time. But the point is quite different: the photon is an oscillating cobination of an electric and a magnetic field and the electron has an electric and a magnetic field around it. How do these two fields of the two particles act on each other within the effective radius?

What will happen to "unconsumed part" of photon?

The absorbed photon leaves the electron again and has a longer/shorter wavelength and the electron is faster/slower afterwards than before.

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