Knowledge Bank

Double quantum light scattering by a system of molecules is discussed in this talk. Expressions have been obtained for the scattered light intensity considering both the coherent and incoherent contributions. In that coherent contributions are also considered in this treatment, it goes beyond the scope of previous studies. It is shown that one does not obtain additional information by using anything but linearly polarized light or by looking in any direction but the classic $90\circ$ angle. According to the present results, the apparent discrepancy between the observed value of $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}/3$ for the depolarization ratio for $CCl4$ and the value to be expected from theory may be due to the fact that the coherent contribution had been neglected in previous theoretical considerations.