Acta Physica et Chemica Tomus XII. Fasciculi 1-2 [antikvár]

FURTHER INVESTIGATIONS ON DEGREE OF POLARIZATION IN VISCOUS QUENCHED FLUORESCENT SOLUTIONS By J. HEVESI Institute of Experimental Physics, Attila József University, Szeged (Received December 15, 1965) The earlier statement that Perrin-Levshin's linear relation is formally not fulfilled in the case of viscous quenched solutions is supported by further experimental results. It is shown that in viscous quenched systems the relation i/p=f(Tltjv) is not linear. The validity of the expression obtained for the relation between these quantities is checked by experimental results. 1. Introduction It has been shown in an earlier paper [1] that the linear relation 1 1 Í 1 1 I k-T — -—+--T--T (1) P Po {Po 3 )v% introduced by Perrin and Levshin [2] apparently looses its validity in the case of viscous solutions containing „dynamic quenchers", inasmuch as the function llp=f(T/t/„) ceases to be linear. (In (1) p means the true degree of polarization, Po the fundamental polarization, k Boltzmann's constant, T absolute temperature, v volume of the fluorescent molecule, r\v viscosity of solution and x lifetime of excited state.) This statement was supported by experimental data obtained for viscous solutions of fluorescein quenched by KI. In that investigations the viscosity of solutions was varied by changing the temperature. The true degree of polarization p was determined from the degree of polarization p' obtained experimentally with the relation P = 1-a: (1-0,6/) (2) given by Budô and Ketskeméty [3], (In (2) x = ¦ t] is a correction factor for the effect of secundary fluorescence [4]; y.n) and t] can be determined by spectrophotometry measurements.) The experimental results obtained in this way actually showed the relation different from linear, which was to be expected (see Fig. 2 in [2]). A quantitative relation was proposed [5] between p and T/riv instead of the qualitative connection given in [1]. In the present paper the validity of this quantitative relation is supported by experimental results.