After being excited by a photon, an electron of a photoactive molecule jumps to a higher electronic state. When it relaxes, the molecule emits a photon (in simple terms). How is this photon "generated"? Photons are particle/waves, right? So somehow this particle has to form. I picture it in a way similar to when you blow through a ring of soap-water and a bubble forms.

How does the photon really form?

  • $\begingroup$ When Particle meets it's antiparticle (for example electron meets positron) they will annihilate and 'generate' two photons: Example that shows electron-positron annihilation: $ e^+e^-\rightarrow \gamma\gamma $ And Energy of that photon will be $E=2m_ec^2$ ($2m_e$ because we have two particles(electron an positron) which have same mass) and the frequency of that photon is: $ f = \frac{2m_ec^2}{h} $ $\endgroup$ – Gigi Butbaia May 2 '14 at 14:05
  • $\begingroup$ And when electron goes from higher energy state to lower energy state it emits light, because at higher energy state it has more energy than in lower energy state, so when it goes down it has to 'lose' energy in order to go down so it emits light(photon) $\endgroup$ – Gigi Butbaia May 2 '14 at 14:11
  • $\begingroup$ I appreciate your response but you're not saying anything that I havn't said in my post. $\endgroup$ – TMOTTM May 4 '14 at 18:57

It is a quantum mechanical process. One could go on an explanation with photon creation and annihilation operators , but there is not much intuition into that.

One can start classically, an accelerating charge radiates an electromagnetic wave. The Bohr atom was proposed, i.e. the quantization of energy levels, in order to explain why a circulating electron would not radiate its energy away and fall into the nucleus. What the Bohr model does, instead of the electron radiating continuously, it can only radiate in quanta of electromagnetic energy , when falling into an empty energy level. Otherwise it is in a stable orbit ( Bohr model has orbits). This quantum of electromagnetic energy is called a photon. It is a quantum mechanical entity, sometimes appearing as a particle and sometimes when in large numbers building up the classical electromagnetic wave.

In the Schrodinger equation solution of the hydrogen atom the same logic holds, except the electron is in an orbital and not an orbit.


As far as I know, quantum mechanics / quantum electrodynamics doesn't have an answer to your question. It can tell you that it does happen, how often, where, under what conditions, the energy of the photon, etc, but as to the detailed step-by-step mechanism, such as we are used to in ordinary everyday experience, quantum mechanics is silent. Frustrating, isn't it?


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.