Raman waveshift converter
Raman spectroscopy is a powerful analytical technique used to identify molecular structures and characterize materials through their unique vibrational fingerprints. Raman spectra are typically plotted as Raman shift (cm⁻¹), which represents the energy difference between the excitation laser and the scattered light.
Although Raman shift is expressed in the same unit as the wavenumber scale used in infrared (IR) spectroscopy, the two quantities are not identical. IR spectra are plotted versus the absolute wavenumber of the absorbed light, whereas Raman spectra are plotted relative to the excitation laser wavelength. This makes Raman shift a convenient way to compare spectra acquired using different laser wavelengths.
Use the Raman shift calculator below to convert range and resolution between wavelength in nm and Raman shift in cm-1.
What is Raman shift?
When monochromatic laser light illuminates a sample, most photons are scattered without changing energy. This process is known as Rayleigh scattering. A small fraction of photons interact with molecular vibrations and emerge with slightly different energies. These energy differences form the basis of Raman spectroscopy.
Because photon energy is related to wavelength according to
| E = | hc |
| λ |
where h is Planck’s constant, c is the speed of light, and λ is the wavelength, even small wavelength differences correspond to measurable vibrational energy changes.
Rather than displaying the scattered wavelength directly, Raman spectra are normally plotted as Raman shift in units of cm⁻¹. This shift represents the difference between the laser wavenumber and the scattered-light wavenumber.
The result is a universal vibrational scale that allows spectra recorded using 532 nm, 633 nm, 785 nm, 830 nm, or 1064 nm excitation lasers to be compared directly.
Raman shift formulas
The Raman shift Δω can be calculated from the excitation laser wavelength λlaser and the measured scattered wavelength λ according to:
| Δω [cm-1] = 107 ( | 1 | – | 1 | ) ; λ [nm] |
| λlaser | λ |
The Raman resolution δω can be calculated from the spectral wavelength resolution δλ and the measured scattered wavelength λ according to:
| δω [cm-1] ≈ 107 | δλ | ; λ [nm] |
| λ2 |
To calculate the wavelength and resolution in nm from the Raman shift and resolution in cm-1 the following formulas can be used:
| λ [nm] = 1 / ( | 1 | – | Δω | ) ; Δω [cm-1] |
| λlaser | 107 |
| δλ [nm] ≈ | δωλ2 | ; δω [cm-1] |
| 107 |
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