What Is an Absorption Spectrum?

Absorption spectrum refers to the spectrum produced by a substance absorbing photons and transitioning from a low energy level to a high energy level. The absorption spectrum can be a linear spectrum or an absorption band. Studying absorption spectra can understand the structure and motion of atoms, molecules, and many other substances, and how they interact with electromagnetic fields or particles. ^[1]

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Absorption spectroscopy is widely used in the composition analysis and structural analysis of materials, as well as various scientific research work. There are several ways to observe the absorption spectrum:

Use a light source with a continuous spectrum, such as incandescent, continuous-spectrum infrared light sources. After passing through the sample, the light is recorded by a spectrometer, and a dark absorption spectrum is displayed on a continuous white light background.

The light emitted by the light source passes through a spectroscope first, and becomes quasi-monochromatic light. Adjust the spectroscopic instrument so that the frequency of light is continuously scanned through the sample and recorded to obtain a linear shape of the absorption spectrum.

Use a continuously tunable laser as the light source, and directly record the absorption spectrum without using a spectroscopic instrument. The development of laser technology has greatly promoted the research on absorption spectroscopy methods, and now has the laser absorption spectroscopy technology required to obtain extremely high resolution and sensitivity (see Laser Spectroscopy). ^[1]