B Understanding Excitation Energy in Atoms: Threshold Values and Potential States

[Bennet]

My physics textbook says roughly that:

Within an atom; when electrons are raised from the ground state to the energy levels that comprise their various atomic spectra, the potential energy carried by either a photon or an electron (or other) must exactly match these quantitative energy levels to excite the electrons into a raised potential state.

And if the energy of the incident "entity" does not match these critical values then nothing happens at all?

Yet it seems to be the case that to cause Ionisation of the same atom, the specific level of energy can be completely imprecise as long as it meets the requirements of being above a threshold value

Is this the case or have I got the wrong end of the stick?

Many thanks for any help provided. If stupid please be kind as never been on a forum before. Thanks.

(Detailed insight beyond high school level would be greatly appreciated if applicable.)

 

[Dale]

Yet it seems to be the case that to cause Ionisation of the same atom, the specific level of energy can be completely imprecise as long as it meets the requirements of being above a threshold value

I moved your question to the quantum section where I think it will get attention from people who can help with the math. However, what you say here is essentially correct. The energy levels of bound states are quantized, but unbound states are not.

 

[Bennet]

thanks

 

[blue_leaf77]

an electron (or other) must exactly match these quantitative energy levels to excite the electrons into a raised potential state.

Photon energy doesn't have to be exactly equal to the energy difference with some excited state for something to happen inside an atom. In general, interaction between atom and EM field causes a disturbance in which different energy eigenfunctions are coupled. It's just that the probability for the atom to end up in a level whose energy difference is closest to the photon energy is higher than those to end up in any other levels.