1. NEEP 541 – Electronic Stopping
Fall 2003
Jake Blanchard

2. Outline Electronic Stopping Definitions Theoretical Models
Empirical Models

3. Electronic Stopping
At high energies, heavy particles lose energy to electrons faster than they lose it to collisions with atoms
This causes heating, not damage
This energy loss reduces the number of displacements
Mechanism relies on stripping of electrons

4. Electronic Stopping
Find minimum energy (Ec) below which a moving atom cannot transfer enough energy to electron to remove it from bound state
I=binding energy of electron (2 eV)
at energies above Ec, stopping dominated by electronic stopping

5. Electronic Stopping
High velocity strips moving atoms of electrons, creating net charge
Hence, atom has charge
This leads to coulomb reactions with lattice electrons

6. Electronic Stopping
Detailed analysis gives another factor of 2

7. Electronic Stopping
For E>ET,
Bethe’s Formula

8. Low Energy Stopping
At low energy, only valence electrons are available
Ve0
V10
2V10+Ve0= Vef
V10

9. Low Energy Stopping
Only electrons with velocity within this value of Fermi velocity can be removed

10. Low Energy

11. Low Energy

12. Summary

13. Ni target

14. Empirical Stopping Powers
Wilson et al, Phys. Rev. B, 15(5), 1977, 2458.

15. Empirical Electronic Stopping

16. Copper-Copper
total
electronic
nuclear

17. Proton on Copper