spectroscopy
Meaning of spectroscopy: Reading what a substance is made of by seeing which wavelengths it absorbs, emits or bends, since every material has a signature.
Definition of spectroscopy
Spectroscopy is the study of how matter interacts with electromagnetic radiation across a range of wavelengths. Every substance absorbs, emits or scatters particular wavelengths and leaves others untouched, so the resulting pattern acts as a chemical fingerprint. Measuring that pattern identifies what a sample contains and often how much, without necessarily destroying the sample.
How does it identify a substance?
Electrons and chemical bonds can only hold certain fixed amounts of energy. A packet of radiation is absorbed only when its energy matches a gap the molecule can accept, and each kind of molecule has its own set of gaps. Shine a range of wavelengths through a sample and the ones that match are removed, leaving dark lines in the spectrum. The position of those lines names the substance and their depth indicates how much is present. Emission works the other way round: a sample given energy releases it again at its own characteristic wavelengths as it settles back down. Either way the pattern belongs to the substance and not to the instrument, which is what makes the reading transferable between laboratories.
What are the main types?
| Type | What is measured | Common use |
|---|---|---|
| Absorption | Wavelengths taken up | Blood oxygen measurement, laboratory assays |
| Fluorescence | Light given off after excitation | Labeling molecules in tissue |
| Raman | Light scattered with shifted energy | Chemical identification, research imaging |
| Magnetic resonance | Radio signals from atomic nuclei | Chemical makeup within a scanned region |
Where is it used in medicine?
The commonest example sits on a fingertip. A pulse oximeter shines two wavelengths through the finger and compares how much each is absorbed, because oxygen-carrying and oxygen-free hemoglobin absorb differently. Clinical chemistry analyzers measure most blood constituents by absorption in a cuvette. Magnetic resonance spectroscopy adds chemical information to an ordinary scan, showing the balance of certain molecules inside a region of brain rather than just its shape, which contributes to diagnosis in some conditions. Research methods such as optical spectroscopy are being examined for reading tissue during surgery, in the hope of telling normal from abnormal without waiting for a sample to be processed.
Used in a sentence
Magnetic resonance spectroscopy was added to characterize the lesion.
Good to know
Spectroscopy identifies chemical composition rather than structure, which is why magnetic resonance spectroscopy is reported alongside conventional images rather than in place of them.
Word origin
Where “spectroscopy” comes from
Joins the Latin spectrum, meaning appearance or image, with the Greek skopein, to look at.