Molecular interactions and correlation phenomena between pressure shift and solvent shift: a spectral hole-burning study

We measured the pressure shift of spectral holes for four probe molecules, which differed in size, polarity, and charge, as a function of burn frequency. The solvent was in all cases the same, namely, ethanol/methanol glass. We found that the pressure shift depends in a linear fashion on burn frequency and that the associated slope is uniform despite the variation in the solute-solvent interaction. It seems to be a property of the solvent, solely. These findings can be well understood by assuming that the pressure-induced line shift is proportional to the solvent shift. In this case, the compressibility of the host glass follows directly from the slope of the pressure shift vs frequency data