110 Hyperfine structure and isotope shift
Fig. 6.9The projection of the contri-
butions to the magnetic moment from
the atomic electrons alongF. The mag-
netic moment of the nucleus is negligi-
ble in comparison.
Fig. 6.10The Zeeman effect on the
hyperfine structure of the ground level
of hydrogen 1s^2 S 1 / 2 .The interval be-
tween theF =0andF = 1 levels
isA, as shown in Fig. 6.3. The zero
of the energy scale has been chosen to
be midway between the levels at zero
field, which is convenient for the cal-
culations in the text. (The two states
withMF= 0 in the low-field regime
are mixed by the perturbation and then
move apart as the magnetic flux density
increases.) The quantityx=μBB/Ais
plotted on the horizontal axis and the
low- and high-field regimes correspond
tox1andx 1. Low field High field
12001− 16.3.2 Zeeman effect of a strong field,μBB>A
Astrongfieldisonewheretheinteractionwiththeexternalfield,in
eqn 6.28, is greater thanAI·J. This can readily be achieved for hy-
perfine structures since the Zeeman energyμBBin a field of 1 T is
about 6× 10 −^5 eV (corresponding to a frequency of 14 GHz), which is
greater than all but the largest hyperfine structures in the ground con-
figurations of heavy elements (see Fig. 6.7).^26 In this regimeFis not a(^26) But smaller than the fine structure
of the first excited state, except for
the lightest elements. High-lying levels,
however, have smaller fine structure.