A New Approach to Determining the Spectral Light Absorption of Seawater by a Conical Reflecting Cuvette with an Integrating Sphere

Determining the light spectral absorption in the sea always encounters difficulties in collecting at the receiving device simul taneously both the rays that have traveled a certain distance in the medium after absorption and all the photons scattered along this path. In the currently used methods, it is not possible to collect all the scattered rays, so it is necessary to take into account the effect of lost photons on the absorption value through theoretical modeling and subsequent correction of the values. A new approach to determining the seawaters spectral absorption of light is proposed by passing a diverging beam through the measured medium placed in a double-walled conical reflecting cuvette with an integrating sphere as a light-receiving collector. By using a diverging beam in a conical quartz cuvette, it was possible to extend it and, thus, ensure the determination of spectral absorption of light in a larger range of seawaters transparency. To compensate the influence of the diffuse radiation of the sphere returning to the double-walled cuvette on the absorption value, a two-beam scheme with normalization to the reference flux was used. It is shown that the new approach makes it possible to redirect almost all scattered light to the receiver and thus minimize errors in determining light absorption in a weakly absorbing medium. To quantify the advantages of the new method, calculations were carried out of the geometric parameters of the scattered light propagation for a double-walled conical quartz cuvette.