IR Spectrum Simulator Inputs
Example Data Table
| Example Peak | Center (cm⁻¹) | Width | Intensity | Typical Meaning |
|---|---|---|---|---|
| Broad O-H | 3350 | 220 | 0.85 | Alcohol or hydrogen-bonded O-H region |
| sp3 C-H | 2930 | 80 | 0.35 | Alkane C-H stretching band |
| C=O | 1715 | 45 | 1.25 | Strong carbonyl stretching band |
| C-O | 1105 | 60 | 0.80 | Alcohol, ester, or ether C-O stretch |
These rows show one practical setup for a broad alcohol-like spectrum with a carbonyl contribution and a fingerprint-region C-O band.
Formula Used
G(ν) = exp[ -4 ln(2) × ((ν - ν₀)² / w²) ]
L(ν) = 1 / [ 1 + 4 × ((ν - ν₀)² / w²) ]
P(ν) = ηL(ν) + (1 - η)G(ν)
A(ν) = baseline + Σ [ intensityᵢ × profileᵢ(ν) ] + noise
T(%) = 100 × 10-A(ν)
The calculator simulates each peak as a band centered at ν₀ with a full width at half maximum of w. It adds all enabled bands, then applies baseline drift, optional noise, and optional smoothing.
How to Use This Calculator
- Choose whether you want absorbance or transmittance output.
- Select a line-shape model: Gaussian, Lorentzian, or blended pseudo-Voigt.
- Set the spectral window, usually 4000 to 400 cm⁻¹ for a standard IR view.
- Adjust baseline offset, slope, noise, smoothing, and seed if needed.
- Enable peak rows and enter a label, center, width, and intensity for each band.
- Submit the form to generate the chart, summary metrics, and peak assignment table.
- Use the CSV export for raw spectral data and the PDF export for a quick report.
Frequently Asked Questions
1) What does this simulator actually model?
It builds a synthetic infrared spectrum from user-defined peaks, then applies baseline drift, optional noise, smoothing, and either transmittance or absorbance output conversion.
2) Why does the x-axis run from high to low wavenumber?
That direction follows standard IR plotting convention. Spectra are commonly displayed from about 4000 cm⁻¹ on the left to lower values on the right.
3) What does peak width mean here?
Width represents full width at half maximum. Larger values make broader bands, which is useful for hydrogen-bonded O-H regions, overlapping envelopes, or low-resolution signals.
4) When should I use Gaussian or Lorentzian shapes?
Gaussian bands are often used for broadened experimental features. Lorentzian bands create sharper wings. The blended option is a flexible compromise for classroom and exploratory simulations.
5) Is the functional group assignment definitive?
No. The assignments are teaching-oriented hints based on common wavenumber ranges. Real identification also depends on exact band shape, neighboring peaks, sample type, and literature references.
6) Why can two very different molecules look similar here?
Because the simulator is range-based and peak-driven. It does not include full molecular quantum calculations, coupling effects, solvent effects, or instrument-specific distortions.
7) What does the integrated area tell me?
It summarizes total absorbance across the simulated range. Larger values generally reflect stronger or broader bands, but it should be treated as a comparative simulation metric.
8) Why add smoothing and noise controls?
Noise makes the spectrum look less idealized. Smoothing helps mimic post-processing or reveal broad trends after random variation is introduced.