  Phenanthrene, a three ring aromatic hydrocarbon, is used as a model substance
for study of intermolecular interactions in dilute solutions of organic
solvents and water by spectroscopic method. Temperature dependencies of shift
of the S$_2\leftarrow$S$_0$ spectrum of phenanthrene dissolved in apolar
solvents and in liquid water are studied in this work. The spectroscopic data
are used for analysis of the cavity radius $R$ for phenanthrene molecule in
solvents. It is shown that the value of $R$ increases with temperature in
organic solvents. In contrast, for water solution, the value of $R$ initially
grows with temperature increase (in the interval of 273.3-296 K), but becomes
constant at higher temperatures. The changes of water structure in the
neighbourhood of a phenanthrene molecule and probable hypothesis about causes
of $R$ value constancy in high-temperature region are discussed. Conclusion
about strengthening of the water structure in an aqueous cage with phenanthrene
molecule inside is done.
