Simplified Ellipsoids of Revolution

It is instructive to consider the anisotropy decays oblate ellipsoids when die )s( ption and emisaon transition moments are not collinear (P 0). Nonzero angles occur in many floorophores, including indole and 

Now consider excitation when p = 4S, with Pa = Pg= 90. In this case the anisotropy decay is given by 

This is the origin of the stalanent that excitation with It)= O.I results in measurement of the out-of-plane rotatian. When P=4S, the excitation is randomized in the plane of the fluoiopbote, so the in-plane rotation has no further effects. 

Finally, consider excitation with p = S4.7 and ro = 0. Bor this contfftion, r l) remains zero at all times if one of the transitions is aligned with one of die axes. However if die transidans make nonzero angles with the axes, dm r(r) can be nonzero at intermedialB tiines, even with ro = 0. 

Similarly, consider excitation of peryleoe with ro=-4X2. Inidally, nridicr out-t -plane rotadon displaces the emission moment, so the only acdvedqiolwizing rotadon is the in-plane rotation. (Recall that the excited-state populadon is symmetrical around the z-axis.) Once the molecule has 

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