Spectral redshift is affected by many factors, such as solvent, temperature, chromophore and so on. However, I found that when the optical path increased, the absorbance of the inorganic salt solution increased at the same time, with a slight redshift occurred, ~3-10nm.
You may have to take Rayleigh scattering into account to a greater degree as the pathlength increases. Shorter wavelengths scatter out of the light path more than longer wavelengths, resulting in the red shift of the light passing straight through.
Jun Ma It would be nice if you could show as the corresponding spectra - maybe it is a saturation effect, but to say this for sure I would need to see the spectra...
Thank you, Jun Ma ! You have increased the pathlength by a factor of 40, but the absorbance has increased only by a factor of about 4. Have you diluted the solution accordingly? Or am I misunderstanding something?
Really strange - the bands don't look like as if saturation is the problem. Also, for 2 mm pathlength, there is a shoulder which vanishes with increasing pathlength. It might make sense to do band fitting to confirm this. What is the concentration of the NaCl and what would happen if you perform these measurements with in- or decreased NaCl concentration?
What do you mean that the concentration increases? A concentration increase leads indeed to a redshift, see Article Study on the shift of ultraviolet spectra in aqueous solutio...
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