Figure 5.

The geometry of relevant vectors and angles for the LD experiment (measured is A_z − A_x). The stretching axis coincides with the z axis. The long axis of the membrane fragment is supposed to coincide with the z axis. For a pigment in a complex embedded in an oriented membrane, we define a normal, n, and a vector perpendicular to this normal, n_⊥, in the plane of the pigment transition dipole moment, μ, and n. We project the pigment transition dipole moment, μ, on n and n_⊥. The orientation of μ is defined by three angles: (i) between the projection of μ to n_⊥ and the z axis: φ; (ii) between μ and the normal, n: θ; and (iii) between the projection of μ to n and the x axis: δ.