Advanced Absorption Spectrum Tool

Absorption Spectrum Tool

Use the form below to model a smooth absorption spectrum from Beer–Lambert inputs and peak-shape controls.

Sample Name

Concentration (mol/L)

Path Length (cm)

Molar Absorptivity ε (L·mol⁻¹·cm⁻¹)

Primary λmax (nm)

Peak Width FWHM (nm)

Baseline Absorbance

Secondary Peak Ratio (0–1)

Secondary Peak Offset (nm)

Start Wavelength (nm)

End Wavelength (nm)

Step Size (nm)

Example Data Table

Sample	λmax (nm)	Concentration (mol/L)	Path Length (cm)	ε (L·mol⁻¹·cm⁻¹)	Peak Absorbance
Copper Sulfate	620	0.025	1.0	14500	0.3825
Potassium Permanganate	525	0.0008	1.0	2200	1.7600
Nickel Complex	395	0.018	1.0	7800	0.1404
Food Dye	504	0.0015	1.0	98000	1.4700

Formula Used

Beer–Lambert law: A = ε × c × l

Here, A is absorbance, ε is molar absorptivity, c is concentration, and l is path length.

Spectrum model: A(λ) = Abase + Apeak × exp[-0.5 × ((λ − λmax) / σ)²] + Apeak × r × exp[-0.5 × ((λ − λsecondary) / σ₂)²]

The model uses a main Gaussian band and an optional shoulder peak. The shoulder is controlled with the secondary ratio and offset fields.

Width conversion: σ = FWHM / 2.35482

Transmittance conversion: T(%) = 10^−A × 100

Integrated absorbance area: the tool applies trapezoidal integration across the generated wavelength range.

How to Use This Calculator

Enter the sample name for your report and downloads.
Add concentration, path length, and molar absorptivity values.
Set the main peak wavelength and desired FWHM.
Add a baseline absorbance to reflect background signal.
Use secondary ratio and offset to model a shoulder band.
Define the wavelength range and step size.
Press Generate Spectrum to view results above the form.
Inspect the Plotly chart, review the preview table, then export CSV or PDF.

Frequently Asked Questions

1. What does this tool calculate?

It models an absorption spectrum, estimates peak absorbance, computes transmittance, reports integrated area, and creates a wavelength-by-wavelength data table for export.

2. Why is Beer–Lambert law important here?

Beer–Lambert law links concentration, path length, and molar absorptivity to absorbance. It gives the core peak height before the spectral band shape is applied.

3. What does FWHM represent?

FWHM is the full width at half maximum. It describes how broad the main absorption band appears across wavelengths.

4. What is the secondary peak ratio for?

It adds a smaller shoulder or nearby band. This helps mimic real spectra that show asymmetry, overlap, or ligand-field effects.

5. Why can absorbance become very high?

High concentration, long path length, or strong molar absorptivity can drive absorbance upward. Extremely high values may be harder to measure accurately on real instruments.

6. Is the transmittance value measured or calculated?

It is calculated from absorbance using the standard optical relationship. Lower transmittance means stronger light absorption at that wavelength.

7. Can I use this for teaching or lab planning?

Yes. It works well for demonstrations, experiment planning, trend comparison, and quick what-if checks before collecting instrument data.

8. Does this replace spectrophotometer data?

No. It is a modeling and planning tool. Real samples may show solvent effects, scattering, instrument noise, and multiple overlapping transitions.