Bohr Model - Absorbing a Photon with Enough Energy to Ionize the Atom

[flintstones]

Homework Statement

What happens when a photon has more than enough energy to ionize an atom? Can it be absorbed?

Relevant Equations

N/A

I just want to confirm something. You need about 13.6 eV of energy to ionize a hydrogen atom in the ground state.

Can the atom absorb a photon with 15 eV of energy? I think it can. This would free the electron, and the freed electron would move off with a kinetic energy of 15 minus 13.6 eV, correct?

I checked two textbooks and both only say that an atom can only absorb a photon with an energy that corresponds to the difference between the atom's energy levels.

Neither mentions the case where a photon has more than enough energy to ionize an atom, so I just want to make sure I'm not thinking incorrectly.

 

[troglodyte]

E_ph=hf=DeltaE(Atom)+E_kin(electron)

The photon should be completely absorbed.The rest energy goes into the kinetic Energy of the electron after it has leaved the ionised Atom as I stated in the formula above.

 

[kuruman]

Homework Statement:: What happens when a photon has more than enough energy to ionize an atom? Can it be absorbed?
Relevant Equations:: N/A

checked two textbooks and both only say that an atom can only absorb a photon with an energy that corresponds to the difference between the atom's energy levels.

The bound energy levels exist from -13.6 eV to zero. Beyond that, there is continuum of energy levels where the electron can exist. So yes, a 15 eV photon will ionize an electron which will acquire 1.4 eV of kinetic energy.

 

[flintstones]

The bound energy levels exist from -13.6 eV to zero. Beyond that, there is continuum of energy levels where the electron can exist. So yes, a 15 eV photon will ionize an electron which will acquire 1.4 eV of kinetic energy.

Thanks, this is what I thought. But now I'm confused about something else.

Take the sodium atom for example. The energy levels go from approximately -5.1 eV to zero. So photons with an energy of more than 5.1 eV should ionize the atom and be absorbed.

Does this mean ANY photon with an energy of more than 5.1 eV that passes through a sodium atom gets absorbed? Because that doesn't seem right...

 

[kuruman]

It's not as simple as that. Sodium has many more electrons than hydrogen that can be be ionized. They are in energy levels with energies less than -5.1 eV. I would think that any photon with energy more than 5.1 eV could ionize the outer electron.