spectroscopy

Study of spectra (see spectrum) associated with atoms or molecules in the solid, liquid, or gaseous phase. Spectroscopy can be used to identify unknown compounds and is an invaluable tool in science, medicine, and industry (for example, in checking the purity of drugs).

Emission spectroscopy is the study of the characteristic series of sharp lines in the spectrum produced when an element is heated. Thus an unknown mixture can be analysed for its component elements. Related is absorption spectroscopy, dealing with atoms and molecules as they absorb energy in a characteristic way. Again, dark lines can be used for analysis. More detailed structural information can be obtained using infrared spectroscopy (concerned with molecular vibrations) or nuclear magnetic resonance (NMR) spectroscopy (concerned with interactions between adjacent atomic nuclei). Supersonic jet laser beam spectroscopy enables the isolation and study of clusters in the gas phase. A laser vaporizes a small sample, which is cooled in helium, and ejected into an evacuated chamber. The jet of clusters expands supersonically, cooling the clusters to near absolute zero, and stabilizing them for study in a mass spectrometer.