A material's absorption spectrum shows the fraction of incident electromagnetic radiation absorbed by the material over a range of frequencies. Atoms, for example, have absorption lines at wavelengths corresponding to the differences between the energy levels of its atomic orbitals. Each chemical element has a distinct absorption spectrum. Absorption spectra can therefore be used to identify the elements present in a gas or liquid. This method is used in deducing the presence of elements in stars and other gaseous objects which cannot be measured directly. The complete absorption spectrum of a material will depend not only on the atoms present but also how they are combined into molecules, how those molecules are packed together and the environment the material is in (e.g., temperature, pressure, electromagnetic fields and other materials present).

Absorption spectrum observed by the Hubble Space Telescope

[edit] See also

• Fraunhofer lines
• Spectroscopy
• Absorption spectroscopy
• Densitometry
• cf. Emission spectrum
• X-ray absorption spectroscopy
• Absorption (electromagnetic radiation)
• HITRAN

[edit] External links

• Solar absorption spectrum
• Visible Absorption Spectrum Simulation
• Plot Absorption Intensity for many molecules in HITRAN database