MolDraw › Chemistry tools › Raman Spectrum Viewer
Free Raman Spectrum Viewer
Open Raman spectra, turn an nm axis into Raman shift, take away the fluorescence background and cosmic-ray spikes, smooth, pick peaks and see the likely bands. Overlay several spectra. Your files stay on your device.
or drop them here. JCAMP-DX (.jdx, .dx), CSV/TXT (shift or nm, intensity) or SPC. Pick several files to overlay them.
· Examples are simulated and free to reuse. Download the sample .jdx.
Laser and x axis
Clean up
Peaks and likely bands (selected spectrum)
How to use the Raman spectrum viewer
- Open your file(s), or press an example button.
- If the x axis is in nm, pick your laser so the tool can work out the Raman shift.
- Tick Remove spikes to clear cosmic rays, and Savitzky-Golay smooth if the data is noisy.
- Pick a baseline to remove fluorescence. Check the red dashed line sits under the peaks.
- Read the peak table. For carbon samples, read the D, G and 2D check.
- Open more files and tick Normalise to compare them.
- Export a PNG or the cleaned CSV.
Reading a Raman spectrum
The Raman shift is the energy lost by the laser light, in cm⁻¹. It is the same for any laser, so spectra from 532 and 785 nm lasers line up. Bands that change polarisability are strong: C=C, C≡C, S-S, aromatic ring breathing near 1000 cm⁻¹ and symmetric stretches. Polar groups such as C=O and O-H are weak.
Carbon: the G band near 1580 cm⁻¹ comes from sp2 carbon, the D band near 1350 cm⁻¹ needs defects or edges, and the 2D band near 2700 cm⁻¹ shows the number of layers. Silicon gives one sharp band at 520.7 cm⁻¹, which is often used to check the calibration.
Frequently asked questions
Is my data uploaded?
No. Files are read and drawn in your browser only.
Which files can I open?
JCAMP-DX (.jdx, .dx), CSV or TXT with two columns, and Thermo/Galactic SPC (new format). The x axis can be Raman shift in cm-1 or the absolute wavelength in nm.
My file is in nm. How do I get the Raman shift?
Pick your laser (532, 633, 785 or 1064 nm, or type your own). The tool uses shift = 10⁷/λ laser − 10⁷/λ. If the tool did not notice the nm axis, tick File x axis is wavelength in nm.
How do I remove the fluorescence background?
Choose a baseline. Asymmetric least squares (ALS) follows curved backgrounds well: a bigger λ gives a stiffer line. Polynomial fits a smooth curve under the peaks; order 3 to 5 suits most spectra. The red dashed line shows what will be taken away.
What does spike removal do?
Cosmic rays make sharp spikes one or two points wide. The tool finds points that jump far above their neighbours and fills them in from the sides. Real Raman bands are wider, so they are kept. Raise the threshold if a real narrow band is touched.
How are bands assigned?
Each peak is checked against a table of common Raman ranges, such as ring breathing near 1000 cm-1, C=C near 1600, C≡C near 2200, S-S near 510, Si at 520 and the carbon D, G and 2D bands. If C-H stretch peaks are present the tool uses organic groups, otherwise carbon and inorganic bands. Treat the result as a guide.
Can it tell graphene from graphite?
It gives the D/G and 2D/G height ratios and the 2D width. A strong, narrow 2D band (2D/G above about 1.5, width below about 45 cm-1) points to single-layer graphene. A weak or broad 2D band points to multilayer graphene or graphite.