Device for detecting and analyzing wavelengths of electromagnetic radiation, commonly used for molecular spectroscopy; more broadly, any of various instruments in which an emission (as of electromagnetic radiation or particles) is spread out according to some property (as energy or mass) into a spectrum and measurements are made at points or regions along the spectrum. As used in traditional laboratory analysis, a spectrometer includes a radiation source and detection and analysis equipment. Emission spectrometers excite molecules of a sample to higher energy states and analyze the radiation emitted when they decay to the original energy state. Absorption spectrometers pass radiation of known wavelength through a sample, varying the wavelengths to produce a spectrum of results; the detector system reveals to what extent each wavelength is absorbed. Fourier-transform spectrometers resemble absorption spectrometers but use a broad band of radiation; a computer analyzes the output to find the absorption spectrum. Different designs allow study of various kinds of samples over many frequencies, at different temperatures or pressures, or in an electric or magnetic field. Mass spectrometers (see mass spectrometry) spread out the atomic or molecular components in a sample according to their masses and then detect the sorted components.
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