monochromators, because the emission occurs over 4π steradians. As with the other
spectroscopies, the optics behind these analyzers were illustrated in Chap. 5.
8.2.3 X-ray Fluorescence Fine Structure
We mentioned earlier that it is the small changes in X-ray fluorescence line energies
and intensities that make it a valuable tool for chemical information. The primary
sources of fluorescence fine structure are:
• Spin-orbit splitting.
• Multiplet structure.
• Configuration interaction.
• Valence molecular orbitals.
• Magnetic properties.
We now illustrate the effects of these electronic and magnetic properties on the
fluorescence.
8.2.4 Spin-Orbit Coupling Structure
The strongest fluorescence lines involve the exchange of one core hole for another.
For example, in Kα emission, a 1s core hole is filled by a 2p electron, resulting in a
2p vacancy. In this case, the primary fine structure in the fluorescence spectra comes
from spin-orbit coupling in the final-state core holes. For example, coupling of the
S ¼ 1/2 spin and the L ¼ 1 orbital angular momentum splits the 2p
5
final state into
(J ¼ 1/2 or J ¼ 3/2, respectively) 2p
1/2 and 2p
3/2
final states, yielding the Kα 1 and
Kα 2 lines. This is the same spin-orbit coupling that splits L-edge absorption into L 2
and L 3 edges, respectively. This spin-orbit coupling is relatively insensitive to
chemistry (Fig. 8.4), and it yields a relatively constant splitting of lines as well as
constant intensity ratios. It is this chemical insensitivity that allows creation of tables
of emission lines with reasonable accuracy.
8.2.5 Multiplet Structure
For transition metals and lanthanides with partially filled shells of d or f valence
electrons, there is fine structure in the emission that can reveal chemical information
about the ion under investigation. This fine structure generally comes from the
presence of two partially filled shells, which allows for multiple intermediate and
final states. This multiplet interpretation is generally favored for early transition
metal compounds or “Mott-Hubbard insulators” in the solid-state parlance. These
8.2 High-Energy Resolution X-ray Fluorescence (HERXRF)
195
spectroscopies, the optics behind these analyzers were illustrated in Chap. 5.
8.2.3 X-ray Fluorescence Fine Structure
We mentioned earlier that it is the small changes in X-ray fluorescence line energies
and intensities that make it a valuable tool for chemical information. The primary
sources of fluorescence fine structure are:
• Spin-orbit splitting.
• Multiplet structure.
• Configuration interaction.
• Valence molecular orbitals.
• Magnetic properties.
We now illustrate the effects of these electronic and magnetic properties on the
fluorescence.
8.2.4 Spin-Orbit Coupling Structure
The strongest fluorescence lines involve the exchange of one core hole for another.
For example, in Kα emission, a 1s core hole is filled by a 2p electron, resulting in a
2p vacancy. In this case, the primary fine structure in the fluorescence spectra comes
from spin-orbit coupling in the final-state core holes. For example, coupling of the
S ¼ 1/2 spin and the L ¼ 1 orbital angular momentum splits the 2p
5
final state into
(J ¼ 1/2 or J ¼ 3/2, respectively) 2p
1/2 and 2p
3/2
final states, yielding the Kα 1 and
Kα 2 lines. This is the same spin-orbit coupling that splits L-edge absorption into L 2
and L 3 edges, respectively. This spin-orbit coupling is relatively insensitive to
chemistry (Fig. 8.4), and it yields a relatively constant splitting of lines as well as
constant intensity ratios. It is this chemical insensitivity that allows creation of tables
of emission lines with reasonable accuracy.
8.2.5 Multiplet Structure
For transition metals and lanthanides with partially filled shells of d or f valence
electrons, there is fine structure in the emission that can reveal chemical information
about the ion under investigation. This fine structure generally comes from the
presence of two partially filled shells, which allows for multiple intermediate and
final states. This multiplet interpretation is generally favored for early transition
metal compounds or “Mott-Hubbard insulators” in the solid-state parlance. These
8.2 High-Energy Resolution X-ray Fluorescence (HERXRF)
195