A couple of easy questions related to quantum mechanics

[lep11]

Hi, I have a couple of easy questions related to quantum mechanics.

1.Does ionization itself cause radiation and why? I know that when electron collides with an atom it can remove electron if it has enough kinetic energy. And when atom becomes excited and then returns to the ground state it emits a photon. Does ionization emit a photon?

2. What happens to that electron after it has collided with an atom?

 

[tom.stoer]

Does ionization itself cause radiation ?

No. Ionization means that an atom (an electron bound in an atom) absorbes a photon. This process transfers energy to the electron. Radiation is observed when a (free) electron is trapped by an ion i.e. when the electron emits the radiation. For an atom X, the ion X⁺, the electron e^- and the photon γ (representing the radiation) there are two processes

$$X + \gamma \to X^+ + e^-$$

$$X^+ + e^- \to X + \gamma$$

I know that when electron collides with an atom it can remove electron if it has enough kinetic energy. And when atom becomes excited and then returns to the ground state it emits a photon.

You are right, but you should be careful whether you want to talk about excitation / emission / absorpotion of radiation (photons) or excitations via electron - these are two different processes.

Does ionization emit a photon?

No.

What happens to that electron after it has collided with an atom?

It seems that you are talking about something different, namely a process like

$$X + e^- \to X^+ + 2e^-$$

Is this correct?