CHEM2210 Chapter Notes - Chapter 7: Bohr Magneton, Hyperfine Structure, Unpaired Electron
Proportionality factor (g-factor)
where β is the constant, Bohr magneton
Since the energy absorbed by the electron should be exactly the same with
the state energy difference ΔE, ΔE=hv
People can control the microwave frequency v and the magnetic field B. The
other factor, g, is a constant of proportionality, whose value is the property of
the electron in a certain environment.
Hyperfine Interactions
• Another very important factor in EPR is hyperfine interactions.
• Besides the applied magnetic field B0, the compound contains the
unpaired electrons are sensitive to their local “micro” environment.
• Additional information can be obtained from the so-called hyperfine
interaction.
• The nuclei of the atoms in a molecule or complex usually have their
own fine magnetic moments - such magnetic moments occurrence can
produce a local magnetic field intense enough to affect the electron.
• Such interaction between the electron and the nuclei produced local
magnetic field is called the hyperfine interaction.
Then the energy level of the electron can be expressed as:
• a is the hyperfine coupling constant
• mI is the nuclear spin quantum number
Hyperfine interactions can be used to provide a wealth of information about
the sample such as the number and identity of atoms in a molecule or
compound, as well as their distance from the unpaired electron.
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