ESR spectrometry uses microwaves to induce transitions between the magnetic energy levels of unpaired electron spins in paramagnetic substances. ESR is based on atoms, ions, molecules, or molecular fragments with an odd number of electrons exhibiting characteristic magnetic properties due to electron spin and magnetic moment. Since its discovery in 1944, ESR spectroscopy has been exploited as a sensitive and informative technique for investigating paramagnetic species in solids and liquids.

1. ESR Spectrometer
Dr. G. D. HANDE

7. Electron Spin Resonance (ESR) also known
as Electron Magnetic Resonance (EMR) or
Electron Paramagnetic Resonance (EPR) is a
branch of absorption spectroscopy in which
radiations having frequency in the
microwave region (0.04 – 25 cm) is
absorbed by paramagnetic substances to
induce transitions between magnetic energy
levels of electrons with unpaired spins.

9. ESR is based on the fact that atoms,
ions, molecules or molecular
fragments which have an odd number
of electrons exhibit characteristic
magnetic properties.
An electron has a spin and due to
spin there is magnetic moment.

10. Since its discovery in 1944 by
E.K. Zavoisky, EPR spectroscopy
has been exploited as a very
sensitive and informative
technique for the investigation of
different kinds of paramagnetic
species in solid or liquid states.

11. The phenomenon of electron
spin resonance (ESR) is based on the
fact that an electron is a charged
particle.
It spins around its axis and this
causes it to act like a tiny bar
magnet.