Hello everyone,

I’m working on photoacoustic gas sensing, and I’ve encountered a specific formula in a research paper that I’m trying to understand. The formula they use to calculate the imaginary part of the refractive index (κ) is:

κ = 20 × (σ × NA × λ) / (4π × Vm)

where:

• σ is the absorption cross-section,
• NA is Avogadro's number,
• λ is the wavelength of light,
• Vm is the molar volume of the gas.

Research paper: Simulation model and dimensioning of a photoacoustic sensor for the detection of radiation-induced pressure surges

Authors: Thomas Handte, Sebastian Bohm, Boris Gojc, etc.

This formula is similar to the standard formula κ = (α × λ) / (4π), where α is the absorption coefficient. However, the paper includes an additional factor of 20, and I’m unclear about the reasoning behind this.

Does anyone know why this factor of 20 is included? Is it a scaling factor commonly used in photoacoustic studies, or is it specific to the experimental setup of this particular study? Also, are there any references or textbooks that might help explain this?

Any insights would be greatly appreciated.

Thanks in advance!

Best regards,

Saikrishna