Every fluid has its own unique peak of absorbance at a very specific electromagnetic wavelength. In fact this is one of the methods by which lab analysis of Hydrogen Sulphide in the Gas is carried out: absorbance by a specific, identifiable electromagnetic wavelength.
In recent years, it has been more economical to produce lamps, which have a specific “Wavelength On Demand” – “WOD”. The lamp needs to produce the exact “WOD” but it also needs to – not only analyse the Hydrogen Sulphide, but also produce enough energy flux to decompose the matter into Hydrogen and elementary Sulphur.
We did the same, successfully for Hydrogen Sulphide dissolved in water.