Elektronenspinnresonanz

Elektronenspinnresonanz, often abbreviated as ESR or EPR (Electron Paramagnetic Resonance), is a spectroscopic technique used to detect and study species with unpaired electrons. These species, known as free radicals or paramagnetic species, possess a net magnetic moment due to the spin of their unpaired electrons. ESR spectroscopy works by exposing a sample to a magnetic field and then irradiating it with microwave radiation. When the energy of the microwave radiation matches the energy difference between the spin states of the unpaired electrons in the applied magnetic field, absorption of energy occurs. This absorption is detected and forms the ESR spectrum. The position and shape of the signal in the spectrum provide information about the chemical environment and structure of the paramagnetic species. ESR is a highly sensitive technique, capable of detecting very low concentrations of free radicals. It finds applications in various fields, including chemistry, physics, biology, and medicine. For instance, it is used to study reaction mechanisms, investigate the structure of metalloproteins, and assess oxidative stress in biological systems. The fundamental principle relies on the interaction of the electron's magnetic moment with an external magnetic field and microwave radiation, leading to resonant absorption.