spectrometer

A spectrometer is an instrument that measures the properties of light or other signals as a function of wavelength or mass-to-charge ratio. In optical spectroscopy it disperses light into its component wavelengths and records their intensities, yielding a spectrum that can reveal the identity and concentration of substances or provide information about physical conditions. In mass spectrometry, it separates ions by mass-to-charge ratio and measures their abundances.

A typical optical spectrometer includes an entrance slit, a collimator, a dispersive element such as a prism or diffraction grating, focusing optics, and a detector array or photodetector. The dispersive element spreads the signal so that different wavelengths are directed to different positions on the detector. Calibration with known standards allows wavelength assignment and intensity measurement. Resolution depends on slit width, the dispersion, and detector pixel size.

Optical spectrometers cover visible, ultraviolet, and infrared regions and are used in chemical analysis and astronomy. Mass spectrometers, by contrast, separate ions and measure their abundances, providing molecular weights and structural information. Nuclear magnetic resonance (NMR) spectrometers measure resonant frequencies of nuclei in a magnetic field to determine molecular structure.

Spectral data enable material identification, quantitative analysis, environmental monitoring, quality control, and astronomical research. Instrument performance is described by spectral resolution, sensitivity, accuracy, and dynamic range. Data are presented as intensity versus wavelength (or frequency) or mass-to-charge ratio.

The optical spectrometer emerged from work on prism spectroscopy and diffraction gratings in the 19th century, notably by Fraunhofer. Mass spectrometry was developed in the early 20th century. Modern spectrometers often combine dispersion with digital detectors and computer analysis.