I am attaching the absorbance spectra of H2O and D2O for your reference.

Are you getting same ?

Hello, regarding these facts you surely need to show the details of the measured absorption spectrum, e.g. a graph of your study. In the visible range between 200 nm and 800 nm the absorption is rather low (OD < 0.01)

https://commons.wikimedia.org/wiki/File:Absorption_spectrum_of_liquid_water.png

Thanks everyone! The references were very helpful.