2
$\begingroup$

If I placed and electron and a positron at a certain distance apart in a vaccumm, they would attract each other and annihilate producing 2 or more gamma rays. But, what I would like to know is, does the electron and positron emit photons as they are attracted towards each other before they annihilate ?

I am not refering to the virtual photons that are exchanged as they are attracted to each other. I am asking if real photons are emitted by either or both particles as they move towards each other.

An electron will emit photons as it moves towards the nucleus of an atom and drops down the energy levels, but in this case the electron is losing energy in the form of a photon emission. Does the electron and positron lose any energy during their attraction ?

$\endgroup$
  • 1
    $\begingroup$ They are accelerating charges, and as such they should emit E/M radiation. Is that what you are talking about? $\endgroup$ – Floris Mar 5 '16 at 19:53
  • 1
    $\begingroup$ see soft photon $\endgroup$ – AccidentalFourierTransform Mar 5 '16 at 20:13
4
$\begingroup$

When an electron-positron pair approach they can form positronium, a very low mass and very temporary hydrogen-like system. It comes in two forms, ortho- and para-, depending on the relative orientation of the spins. With para-positronium they have opposite orientations; this is the lowest energy or ground state for positronium.

The excited states can, and do emit photons. Very high precision research was done in this field beginning in the early 1950s.

The Wikipedia article gives the energy states and further references: https://en.wikipedia.org/wiki/Positronium

$\endgroup$
1
$\begingroup$

My 2 cents:

If only two gamma rays are produced with each of their energy equaling the rest energy of either e- or e+ (which is 511keV) then, it could possibly mean that there is no net linear momentum, which possibly means that this e+ and e- pair are very very close to each other and after collision, the gamma rays are emitted as per the law of conservation of energy.

If more than two gamma rays are produced then it could possibly mean that these e+ and e- particles are placed at some distance to each other and it results in net linear momentum because of acceleration generated due to their opposite charges leading to emission of a photon (with varied amplitudes).

In some cases neutrinos could also be produced because of the annhilation. What i can't comment or don't know is if the annihilation could produce one or more neutrino–antineutrino pairs.

Thanks

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.