the form of electromagnetic radiation. The spectrum of electromagnetic radiation
extends in a very wide range of energy (and thus radiation frequencies). Various
spectroscopic techniques, when investigating the interaction of electromagnetic
radiation with a matter (absorption or emission, primary or secondary, by the matter
of a part of energy in the form of electromagnetic radiation), use different frequency
ranges of electromagnetic radiation, depending on the studied spectroscopic processes and characteristic for them magnitude of the energy changes (in Fig. 1.1, a
schematic spectrum of electromagnetic radiation with the assignment of radiation
ranges to individual spectroscopic techniques is shown). For example, nuclear
magnetic resonance (NMR) technique [1–3] uses radio frequency radiation of about
10
8 Hz, recording changes in the spin of atomic nucleus (with very small energy
change) in atoms with a nonzero nuclear spin, e.g.,
1 H,
2 H,
6 Li,
7 Li
, 13 C,
29 Si.
Under the influence of the applied external magnetic field, there is a split of energy
levels in these atoms into two groups, depending on whether the nuclear spins are
directed parallel or antiparallel to the direction of the magnetic field. This level
separation is very small, of the order of 0.01 J/mol for the applied field of 1 T,
which corresponds to the radiation frequency of approximately 500 MHz. The
magnitude of energy changes and the associated frequency of electromagnetic
radiation strongly depends on the type of atom and its chemical environment, so
one can get a lot of relevant information about the structure of the material under
investigation.
The method closely related to the NMR is EPR/ESR method (electron paramagnetic resonance/electron spin resonance) [4, 5]—the difference is that in this
method the change in the configuration of the electron spins, and not nuclei, is
studied. The EPR method is based on the presence of permanent magnetic dipoles,
i.e., unpaired electrons (as is the case, e.g., in many transition metals), and examines
the change in spins of such unpaired electrons under the influence of an external
magnetic field. Similarly to NMR, the observed energy changes are also small
(although about 2 orders of magnitude larger) and they are approximately 1 J/mol,
which corresponds to the microwave radiation frequency of approximately
3 Â 10
10 Hz. The obtained data allow analyzing direct environment of a given
atom and hence provide the information on the oxidation state, electron configuration and coordination number of the paramagnetic ion, structural distortions due
Fig. 1.1 Main regions of electromagnetic spectrum with related spectroscopic techniques
2
A. Koleżyński
extends in a very wide range of energy (and thus radiation frequencies). Various
spectroscopic techniques, when investigating the interaction of electromagnetic
radiation with a matter (absorption or emission, primary or secondary, by the matter
of a part of energy in the form of electromagnetic radiation), use different frequency
ranges of electromagnetic radiation, depending on the studied spectroscopic processes and characteristic for them magnitude of the energy changes (in Fig. 1.1, a
schematic spectrum of electromagnetic radiation with the assignment of radiation
ranges to individual spectroscopic techniques is shown). For example, nuclear
magnetic resonance (NMR) technique [1–3] uses radio frequency radiation of about
10
8 Hz, recording changes in the spin of atomic nucleus (with very small energy
change) in atoms with a nonzero nuclear spin, e.g.,
1 H,
2 H,
6 Li,
7 Li
, 13 C,
29 Si.
Under the influence of the applied external magnetic field, there is a split of energy
levels in these atoms into two groups, depending on whether the nuclear spins are
directed parallel or antiparallel to the direction of the magnetic field. This level
separation is very small, of the order of 0.01 J/mol for the applied field of 1 T,
which corresponds to the radiation frequency of approximately 500 MHz. The
magnitude of energy changes and the associated frequency of electromagnetic
radiation strongly depends on the type of atom and its chemical environment, so
one can get a lot of relevant information about the structure of the material under
investigation.
The method closely related to the NMR is EPR/ESR method (electron paramagnetic resonance/electron spin resonance) [4, 5]—the difference is that in this
method the change in the configuration of the electron spins, and not nuclei, is
studied. The EPR method is based on the presence of permanent magnetic dipoles,
i.e., unpaired electrons (as is the case, e.g., in many transition metals), and examines
the change in spins of such unpaired electrons under the influence of an external
magnetic field. Similarly to NMR, the observed energy changes are also small
(although about 2 orders of magnitude larger) and they are approximately 1 J/mol,
which corresponds to the microwave radiation frequency of approximately
3 Â 10
10 Hz. The obtained data allow analyzing direct environment of a given
atom and hence provide the information on the oxidation state, electron configuration and coordination number of the paramagnetic ion, structural distortions due
Fig. 1.1 Main regions of electromagnetic spectrum with related spectroscopic techniques
2
A. Koleżyński