# Question on excitation energy?

1. Sep 11, 2009

### HMS-776

Just wanted to ask a simple question to clarify my thinking.

The Ionization Energy of an atom is said to be the minimum energy required to bring the electron to it's next higher orbit.

Looking at the Oxygen atom's first ionization energy of 13.6eV. Does this mean that any energy level which is 13.6eV or higher will cause the first ionization to take place?

Does this hold true for wavelength? A wavelength which is shorter than the absorbtion wavelength will also cause ionization because the shorter wavelength is stronger?

2. Sep 11, 2009

### xepma

Yea, any energy higher than the required energy will cause the ionization. The higher the energy, the more likely the ionization will take place. Also, the surplus of energy will contribute to the kinetic energy of the electron.

A higher energy automatically means a shorter wavelenght, so this also holds for this, yes.

3. Sep 11, 2009

### Bob S

The ionization energy is the minimum energy that will completely remove the electron out of an atomic orbit and produce a free electron and a negative oxygen ion (with 7 electrons). The maximum wavelength is about 904 Angstroms.

4. Sep 11, 2009

### Redbelly98

Staff Emeritus
There are some misconceptions here, so I'll clear up what I can.

No. The Ionization Energy would completely remove an electron from the atom, as Bob S said.
It is the First Excitation Energy that brings an electron to it's next higher orbital.

That 13.6 eV value is for hydrogen, not oxygen.

This question doesn't really make sense. A photon of 13.6 eV or more energy can cause ionization -- in hydrogen.

Yes, that is true.

5. Sep 12, 2009

### Bob S

From HMS-776
Looking at the Oxygen atom's first ionization energy of 13.6eV. Does this mean that any energy level which is 13.6eV or higher will cause the first ionization to take place?
I stated in another thread by HMS-776 that the ionization energy for one-electron bound states of atoms is
eV = 13.6 Z2/n2.
Oxygen has Z = 8, so the 1S electron binding energy is 870 eV.

6. Sep 12, 2009

### Bob_for_short

???

I think that the upper electron is as bound to the Oxygen ion O+ as the Hydrogen electron to proton so the Oxygen ionization energy should be of the same order (13 eV or so).

The excitation probability or cross section depends on the projectile energy in a specific way: it is zero before the ionization energy threshold, then it grows with the energy, attains a maximum and then decreases.

7. Sep 12, 2009

### Bob S

8. Sep 12, 2009

### Bob_for_short

Last edited: Sep 12, 2009
9. Sep 12, 2009

### Redbelly98

Staff Emeritus