Quantifying absorption strength
Spectriscopic experiments tent to involve passing light of some particular range of wavelength through a sample and recording what gets absorbed
Beer-Lambert law , the absorbance is given by
A = −log10(I/Io) = ε × c × ℓ
I0 is the incident intensity (at a given wavelength),
I is the intensity after passing through the sample,
ε is the molar absorptivity (extinction coefficient) (usually m2 mol-1),
c is the concentration (mol m-3) and
ℓ is the path length through the sample (m)
ε =A / c × ℓ