anti-Stokes lines

physics

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July 16, 2026

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Anti-Stokes lines are specific wavelengths of radiation observed in fluorescence and Raman spectra. They occur when atoms or molecules are already in an excited state, often due to high temperatures. In this scenario, the emitted photon carries more energy than the absorbed photon, resulting in a shorter wavelength for the anti-Stokes line compared to the exciting light. This phenomenon is a deviation from Stokes' law. Coherent anti-Stokes Raman spectroscopy (CARS) utilizes this effect with lasers to generate enhanced signals, allowing for detailed analysis of molecular transitions and even local temperatures in flames and plasmas.123

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Stokes lines
Anti-Stokes lines are found in fluorescence and in Raman spectra when the atoms or molecules of the material are already in an excited state (as when at high temperature). In this case the emitted photon takes the molecule back to the ground state, and thus…
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Anti-Stokes lines are found in fluorescence and in Raman spectra when the atoms or molecules of the material are already in an excited state (as when at high temperature). In this case the emitted photon takes the molecule back to the ground state, and thus…
Read More

spectroscopy
Coherent anti-Stokes Raman spectroscopy (CARS)
_… = 2ν₁ − ν₂ (anti-Stokes) and ν_S = 2ν₂ − ν₁ (Stokes) are produced by wave mixing due to the nonlinear polarization of the medium. While either output signal may be detected, the anti-Stokes frequency is well above ν₁ and has the advantage of being readily separated by optical…
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_… = 2ν₁ − ν₂ (anti-Stokes) and ν_S = 2ν₂ − ν₁ (Stokes) are produced by wave mixing due to the nonlinear polarization of the medium. While either output signal may be detected, the anti-Stokes frequency is well above ν₁ and has the advantage of being readily separated by optical…
Read More