Sketch depicting the relative positions of the emission source, scatterer, and observer. The unit direction vectors pointing from the source to the scatterer, from the scatterer to the observer, and from the source to the observer are represented by n, n′, and n₀ respectively. The distance between the source and the scatterer is denoted as r, while r′ corresponds to the distance between the scatterer and the observer. Additionally, $e_1^{\prime }\text{\hspace{0.17em}and\hspace{0.17em}}{e}_2^{\prime }$ serve as the reference base vectors for polarisation of scattered light. The set of vectors ($e_1^{\prime },e_2^{\prime },n^{\prime }$) form a right-hand coordinate system.