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Who first observed electron-spin resonance in 1944?
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magnetic resonance
Figure 1: Precession of a magnetic dipole moment μ in the presence of a constant field H and a rotating field H′ (see text)
Electron-spin resonance (ESR), also known as electron paramagnetic resonance (EPR), was first observed in 1944 by the Soviet physicist Yevgeny Konstantinovich Zavoysky.12
Zavoysky discovered the phenomenon while conducting experiments on salts of the iron group of elements. His research in radio and microwave spectroscopy demonstrated that unpaired electrons in these materials, which behave like tiny magnets due to their spin, absorb energy from electromagnetic radiation when subjected to a strong, constant magnetic field. This discovery proved to be a significant tool for investigating molecular structures and the nature of chemical bonds.231