![]() Copyright © 2023, Columbia University Press. The Columbia Electronic Encyclopedia, 6th ed. The meaning of VIBRATIONAL SPECTRUM is the part of a molecular spectrum in which the bands arise from quantized changes in the energy of mutual atomic vibrations within the molecule. The Quantum Explanation of Spectral Lines.The instrument used for studying line spectra is the spectroscope. Line spectra of either type are useful in chemical analysis, since they reveal the presence of particular elements. The Fraunhofer lines appearing in the spectrum of the sun are an example of a dark-line spectrum they are caused by the absorption of certain frequencies of light by the cooler, outer layers of the solar atmosphere. It consists of a series of dark lines superimposed on a continuous spectrum, each line corresponding to a frequency where a bright line would appear if the gas were incandescent. When an electron moves from one energy level to the next, it emits or absorbs light of a given wavelength. This high-definition imaging capability does not come at the expense of speed, as NTA benefits from the mature readout technology of visible/NIR cameras, permitting MIR imaging at high frame rates. A dark-line, or absorption, spectrum is the reverse of a bright-line spectrum it is produced when white light containing all frequencies passes through a gas not hot enough to be incandescent. An electron’s spectrum of electromagnetic radiation is released or absorbed as it moves between different energy levels within an atom. If the gas is made incandescent by heat or an electric discharge, the resulting spectrum is a bright-line, or emission, spectrum, consisting of a series of bright lines against a dark background. A gas under low pressure does not produce a continuous spectrum but instead produces a line spectrum, i.e., one composed of individual lines at specific frequencies characteristic of the gas, rather than a continuous band of all frequencies. Examples of a spectrum include the rainbow, the emission colors from the Sun, and the infrared absorption wavelengths from a molecule. Continuous spectra are produced by all incandescent solids and liquids and by gases under high pressure. A spectrum is defined as the characteristic wavelengths of electromagnetic radiation (or a portion thereof) that is emitted or absorbed by an object or substance, atom, or molecule. The spectrum formed from white light contains all colors, or frequencies, and is known as a continuous spectrum. ![]() In addition to visible light, other types of electromagnetic radiation may be spread into a spectrum according to frequency or wavelength. Each different wavelength or frequency of visible light corresponds to a different color, so that the spectrum appears as a band of colors ranging from violet at the short-wavelength (high-frequency) end of the spectrum through indigo, blue, green, yellow, and orange, to red at the long-wavelength (low-frequency) end of the spectrum. Dispersion, the separation of visible light into a spectrum, may be accomplished by means of a prism or a diffraction grating. ![]()
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