2
$\begingroup$

For example let's have the hydrogen atom in its ground state and the electron gets excited by a photon. If we consider relativity the wave function cannot change instantly, right? The process has to be continous. What happens during this process....

Improve this question
$\endgroup$
1
  • $\begingroup$ I think I understand what you're asking. I think that "how is a photon created?" would also be related, but ultimately justified by energy and momentum conservation caused by the electron changing its state $\endgroup$
    – cinico
    Jan 7, 2014 at 18:03

2 Answers 2

Reset to default
2
$\begingroup$

For example let's have the hydrogen atom in its ground state and the electron gets excited by a photon. If we consider relativity the wave function cannot change instantly, right?

In general it can, because wave function is just a description of state, and this can change whenever we want, typically when we know better wave function for the job. Relativity does not reject instant changes in descriptions, it only rejects universal simultaneity of events at different places.

But in the case of absorption of light by an atom, if the wave function satisfies Schroedinger differential equation, it evolves continuously, there is no sudden jump (we do not see what really happens, we just calculate $\psi$, and it evolves continuously.)

The process has to be continous. What happens during this process....

It does not have to be continuous. It could be jump-like. We do not see what is really going on at nano-level. But the continuous description is more satisfactory and general (dif. equation vs. probabilistic rule for jump). What happens in continuous description is that the wave function changes to resemble more higher eigenfunctions, particularly those with the Hamiltonian eigennumbers $E$ close to match with the condition $$ E - E_1 = \hbar \omega $$ where $\omega$ is the angular frequency of the light. Wave function will oscillate in a complicated manner (non-periodically).

Improve this answer
$\endgroup$
2
$\begingroup$

In QM it probably doesn't help to think of an instant - or even of things happening at fixed points in time.

There is an electron if you observe it you will measure a wavefunction. After it absorbs a photon you will measure a different wavefunction.

Improve this answer
$\endgroup$
1
  • 2
    $\begingroup$ Wave function of an electron in an atom cannot be measured. It is just a description of its state. $\endgroup$
    – Ján Lalinský
    Jan 7, 2014 at 17:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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