Chemistry
Two-Photon Absorption Calculator
Compare single and two-photon energies and estimate the relative excitation rate at a given intensity.
Your inputs
Change any value to update the result instantly.
Two-photon transition energy
3.0996 eV
Single photon energy
1.5498 eV
Equivalent one-photon wavelength
400 nm
Photon energy in joules
2.4831 x 10^-19 J
Excitation rate per molecule
1.6219 x 10^13 per second
Intensity scaling
Doubling the intensity gives four times the excitation rate
1 GM = 1 × 10⁻⁵⁰ cm⁴·s per photon per molecule. The rate here uses the plain δI²/(hν)² form for continuous illumination; pulsed lasers need a pulse-shape correction factor for duty cycle.
What this calculator does
Compares one- and two-photon energies for a chosen wavelength and estimates the relative excitation rate.
What your result means
Two photons together deliver the energy of a single photon at half the wavelength, and the rate rises with the square of intensity.
Formula and working
E_photon = hc/λ; ΔE = 2hc/λ; R ∝ δI² / (hν)²
- 1
Collect the inputs
Excitation wavelength λ = 800 nm; Two-photon cross-section δ = 100 GM; Peak intensity I = 1,000,000,000,000 W/cm²
- 2
Apply the formula
E_photon = hc/λ; ΔE = 2hc/λ; R ∝ δI² / (hν)²
- 3
Result
Two-photon transition energy = 3.0996 eV
Frequently asked questions
Symbols and assumptions
- δ
- Two-photon cross-section in GM
- I
- Peak intensity
- h, c
- Planck constant and speed of light
- • Continuous illumination with the plain δI²/(hν)² form.
- • Cross-section entered in Goeppert-Mayer units.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Pulsed lasers need a pulse-shape and duty-cycle correction that is not applied here.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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