What happens when a negative particle faces a positive one?

Question

First let me stress the fact that this question is not a duplicate, there are many similar questions that have missed the point, in particular this

Why doesn't an electron ever hit (and stick on) a proton?

which was led astray by users who basically did not understand what had really been asked.

I'd like to make it clear that I am not looking for a theoretical explanation, but for a concrete description of what actually happens when a negative charge is released in presence of a positive one

if the positive particle is a positron the electron behaves according to Coulomb's law, if the particle is a proton or a nucleus the electron directs itself to the center of the proton and then deviates, I am asking a description of the process and if it is known what force makes the electron deflect from the normal trajectory.

All explanations given in other questions are irrelevant or wrong, like this by John Rennie:

Classically two pointlike particles, an electron and a quark, can never collide because if they're pointlike their frontal area is zero and you can't hit a target that has a zero area.

since a positronn, too, is a pointlike particle

Answer 1

In the image you provide,

You have two oppositely charged centers at ten centimeters apart.

If the charge is carried by a solid mass, of dimensions up to $10^{-10}m$, an angstrom, composed of myriads of molecules the classical electrodynamics theory with the Coulomb potential predicts a direct attraction and neutralization , if they are at rest, a "sticking together once the two masses touch.This has not been falsified by experiments. A scattering track can also be predicted and observed with the classical theory.

There is a classical solution of planetary type orbits which has not been observed at the above dimensions because the experiment would be difficult in the gravitational field of the earth.

From ancient times people tried to imagine the smallest possible dimensions for matter. Atom comes from ancient greek philosophy,and it means "something that cannot be further cut", and in the last two centuries it became clear that at angstrom dimensions the classical electromagnetic theory could not work and a new one was needed.

The basic reason is that if the classical theory would extend to the dimensions of the atom , assuming a positive nucleus and a negative electron, the atoms could not exist with the classical theory. The electron would radiate and fall on the nucleus and no chemistry or spectra would exist. Instead there are stable atoms making up the chemistry of the world as we see it. See this answer of mine for a longer explanation and links.

The coulomb potential is used in quantum mechanics to derive the wavefunction of the system under study and it manages to predict the atomic observations where classical theory fails. In quantum mechanics the particles, electron and proton in your question, do not orbit around each other when near enough, but have orbitals, , stable solutions that give the probability of the electron to exist about the proton at an (x,y,z,t) point.

Observations at the angstrom dimensions have to depend on a theory, and the theory is validated and accepted if it can predict the data.

but for a concrete description of what actually happens when a negative charge is released in presence of a positive one

At the quantum dimensions, at low energies, when a positron hits an electron the two particles annihilate and create two photons. If they are energetic enough the energy can be transformed into numerous pairs of elementary particles, which has been studied with the LEP experiments for example.