Absorption band

An absorption band is a range of wavelengths or frequencies over which a substance absorbs electromagnetic radiation. It can arise from molecular or atomic transitions and may broaden through interactions and measurement conditions.

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Electronic transition: A change in an atom or molecule's electronic state caused by absorbing or emitting energy. Electronic transitions produce absorption bands in ultraviolet and visible spectra.
Electromagnetic spectrum: The full range of electromagnetic radiation, organized by frequency or wavelength. Absorption bands occupy particular regions of this spectrum.
Infrared spectroscopy: A method that studies how matter absorbs infrared radiation to reveal molecular vibrations and chemical environments. Infrared bands help identify functional groups and molecular structures.
Emission line: A narrow spectral feature produced when matter emits radiation at particular frequencies or wavelengths. Emission adds radiation at selected positions where absorption removes it.
Vibrational transition: A change between quantized vibrational energy levels in a molecule. Molecular vibrations generate characteristic infrared absorption bands.
Wavelength: The spatial period of a wave, measured between successive points in the same phase. Bands are commonly specified by the wavelengths they cover.
Ultraviolet–visible spectroscopy: A method that measures absorption of ultraviolet and visible light by matter. Its bands reveal electronic transitions and support concentration measurements.
Absorption line: A narrow reduction in a continuous spectrum caused by absorption at a limited range of wavelengths or frequencies. A line is narrower than the broader feature called a band.
Rotational transition: A change between quantized rotational energy levels of an atom or molecule. Rotational transitions contribute fine structure to molecular absorption spectra.
Frequency: The number of cycles of a periodic signal per unit time. Frequency gives an alternative coordinate for locating an absorption band.