5.6 Summary 93BSLFig. 5.14The Paschen–Back effect oc-
curs in a strong external magnetic field.
The spin and orbital angular momen-
tum precess independently about the
magnetic field. The states have ener-
gies given byEPB=μBB(ML+2MS).5.6 Summary
Figure 5.15 shows the different layers of structure in a case where the
LS-coupling scheme is a good approximation, i.e. the residual electro-
static interaction dominates the two magnetic interactions (spin–orbit
and with an external magnetic field). The spin–orbit interaction splits
terms into differentJlevels. The Zeeman effect of a weak magnetic
field splits the levels into states of givenMJ, that are also referred to as
Zeeman sub-levels.
There are various ways in which this simple picture can break down.
(a) Configuration mixing occurs if the residual electrostatic interaction
−
−
−−Fig. 5.15The hierarchy of atomic structure for the 3s3p configuration of an alkaline earth metal atom.