Infrared (IR) radiation is used in spectroscopy to study the molecular composition and structure of substances by analyzing how they absorb IR light. Here’s how it works:
- Principle
- Molecules can vibrate in different ways (stretching, bending, twisting).
- Each type of bond and vibration absorbs IR radiation at specific wavelengths.
- This produces a unique absorption pattern — like a “fingerprint” for that molecule.
- Process
- A sample is exposed to a range of IR wavelengths.
- The spectrometer measures which wavelengths are absorbed and which pass through.
- The result is an IR spectrum: a graph showing absorption peaks at characteristic wavelengths.
- Types of IR Spectroscopy
- Near-IR (NIR): 0.75–2.5 μm, used for rapid analysis of food, agriculture, and pharmaceuticals.
- Mid-IR (MIR): 2.5–25 μm, used for detailed molecular fingerprinting (most common type).
- Far-IR (FIR): 25–1,000 μm, used for studying heavy atoms and lattice vibrations in solids.
- Applications
- Identifying unknown compounds.
- Checking purity of chemicals.
- Monitoring industrial processes.
- Analyzing atmospheric gases in environmental science.