  We adduce new arguments for the significance of so-called 1.5- (or
sesquialteral) molecular light scattering in one-component fluids. For this
purpose, we analyze its effect on the Landau-Placzek ratio for the critical
opalescence spectrum. The results obtained are used to reveal experimental data
which can be interpreted as evidence for its existence and to evaluate both the
relative magnitude and the sign of the 1.5-scattering contribution.
