Fig. 1 illustrates a technique for measuring laser Raman spectra of materials immersed in a medium, which provides spectra of medium molecules absorbed in materials without interference due to the surrounding medium. The technique can be applied to studying absorbed medium molecules in swollen or gel-like materials, the absorption equilibrium, interactions of matrix materials with medium molecules therein such as water in biomolecules, molecular structure changes in materials accompanied by swelling, etc. The uniqueness of the technique is that the amount of absorbed medium molecules in materials in equilibrium with the surrounding medium can be measured without disturbance from the medium and the time dependence of the absorption process can be followed if it is not too rapid. The amount of absorbed medium molecules can be easily determined by choosing a suitable band of the material as an internal standard.
Reikichi Iwamoto, "Laser Raman Study of Absorbed Medium Molecules without Interference from the Surrounding Medium," Appl. Spectrosc. 33, 55-56 (1979)