1. Last hour: Orbit magnetism
Classical picture: electron orbiting nucleus acts like a current loop, generating magnetic dipole moment
For orbiting electron:
With definition of the Bohr magneton as the magnitude of the magnetic moment generated by an electron with angular momentum ħ:

2. Consequence: replace with .
Transformation of reference frame from nucleus at rest (left) to electron at rest (right).
Consequence: replace with
(from Haken & Wolf “Atom- und Quantenphysik”)

3. Fine structure splitting in the Na 2P term
no spin-orbit
interaction
spin-orbit
interaction
2P3/2
a/2 2P -a
2P1/2

4. Learning Goals for Chapter 21 – Atomic Structure and Term Values
After this chapter, the related homework problems, and reading the relevant parts of the textbook, you should be able to:
assign configurations, terms and levels to the appropriate parts of the Hamiltonian of a multielectron atom;
couple angular momenta in a multielectron atom;
explain the assumptions made in LS coupling and in JJ coupling;
construct atomic term symbols and qualitatively evaluate their relative energies;
calculate the magnetic moment of an atom and its spin and orbital parts;
explain the relation between magnetic moment and angular momentum;
construct the Hamiltonian for atoms in external magnetic or electric fields.