What types of atoms does EPR typically study?

Electron Paramagnetic Resonance (EPR), also commonly known as Electron Spin Resonance (ESR), is a powerful spectroscopic technique used to study materials with unpaired electrons. The primary focus of EPR is on paramagnetic species, which contain unpaired electrons that can be influenced by an external magnetic field.

In paramagnetic species, the presence of unpaired electrons results in distinct magnetic properties that can be detected using EPR. When these species are placed in a magnetic field, the unpaired electrons undergo transitions between different spin states when energy from microwave radiation is absorbed. This property is what makes EPR an effective tool for studying the electronic structures and dynamics of various paramagnetic species, including transition metal ions, free radicals, and defects in solids.

In contrast, diamagnetic species do not possess unpaired electrons and do not exhibit the same magnetic behavior, making them unsuitable for study by EPR. Noble gases typically do not have unpaired electrons either, which further rules them out from being studied with this method. Isotopes, while they can influence certain properties in a system, do not directly correlate with the primary focus of EPR, which is determined by the presence of unpaired electrons.

Thus, EPR is primarily utilized for