Rotational Depolarization of Fluorescence of Prolate Molecules

The theory of rotational depolarization of fluorescence, taking into account the inertial effect, has been verified experimentally for two angular velocity autocorrelation functions obtained for both the approximate and the exact Langevin equation. To this end, the emission anisotropy was investigated as a function of viscosity for PPO, POPOP, and α-NOPON in liquid n-paraffins (from « = 5 to n = 11) at 304.5 K. For these three luminescent molecules with mean lifetimes of about 1 ns, and the viscosities ranging from 0.22 to 0.9 cP, no essential difference was found between the experiment and the theory for the angular velocity autocorrelation functions employed.

Influence of Quenching upon the Rotational Depolarization of Fluorescence

The theory of the rotational depolarization of fluorescence taking into account the inertial effect was verified experimentally on the example of 2,2'-p-phenylenebis(5-phenyloxazole) (POPOP), 2,2'-p-phenylenebis(4-methyl-5-phenyloxazole) 2MPOPOP), p-bis[2-(5-α-naphthyloxazolyl)]- benzene (α-NOPON), diphenylenestilbene (DPS) and 1,6-diphenylhexatriene (DPH) in cyclohexane by the method of quenching with nitrobenzene. The volumes obtained for the centers and moments of inertia are lower than those obtained by the use of solvents of different viscosities, but they still refer to the solvated molecules.