original_query: What is electron paramagnetic resonance (EPR) spectroscopy used for?
query: What is electron paramagnetic resonance (EPR) spectroscopy used for?
answer: EPR spectroscopy is used to detect and identify free radicals and paramagnetic centers in various states (solid, liquid, gas).  It finds applications in biology, chemistry, physics, medical research, material characterization, and archaeology (e.g., dating materials). Specific uses include studying chemical reactions, characterizing paramagnetic complexes in catalysis, and measuring microviscosity and micropolarity in drug delivery systems.