Simulation · on-site
IR spectrum simulator
Overlay real measured spectra (NIST gas-phase FTIR) and reconstructed band profiles (from referenced literature positions) — entirely in your browser, no upload, no external service. Experimental traces are genuine measurements; reconstructions show band positions and pattern, not quantitative absorbance. Plotted as % transmittance (each curve normalised to fill the panel).
How to use it for research
Hit NIST set to load real measured spectra and validate the band atlas against measurement — note these are gas-phase, so carbonyls sit higher than the liquid-phase textbook values (acetone ν(C=O) ≈ 1736, acetic-acid monomer ≈ 1790, vs ~1715 in the condensed phase), and benzene's strong C–H oop nails ~673. Overlay an α-helix and β-sheet for the amide I shift (1654 vs 1630), or B-DNA / A / Z for the phosphate νas(PO₂⁻) marker (1225 → 1240 → 1215). Narrow the linewidth to resolve close bands; widen to mimic condensed-phase broadening.
What is measured vs reconstructed
Experimental curves are genuine FTIR spectra from the NIST Chemistry WebBook (SRD 69, gas phase) — 18 small molecules spanning the functional groups. Reconstructed curves (amino acids, nucleotides, conformers, secondary structures) are Lorentzian profiles built from tabulated literature peak positions — band positions and pattern, not quantitative intensities. NIST gas-phase coverage does not extend to involatile amino acids / nucleotides, so those remain reconstructions; first-principles spectra for arbitrary structures use the GFN2-xTB pipeline (see computation).