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Nonexponential Phosphorescence Decay of Benzene
1.T. E. Martin and A. H. Kalantar, J. Chem. Phys. 48, 4996 (1968).
2.T. E. Martin and A. H. Kalantar, J. Phys. Chem. 72, 2265 (1968).
3.V. Ermolaev, Usp. Fiz. Nauk 80, 3 (1963)
3.[V. Ermolaev, Sov. Phys.‐Usp. 6, 333 (1963)].
4.T. Förster, Discussions Faraday Soc. 27, 7 (1959).
5.A. Sternlicht, G. C. Nieman, and G. W. Robinson, J. Chem. Phys. 38, 1326 (1963).
6.R. E. Kellogg, J. Chem. Phys. 41, 3046 (1964).
7.T. S. Godfrey and G. Porter, Trans. Faraday Soc. 62, 7 (1966).
8.J. D. Spangler and H. Sponer, Spectrochim. Acta 19, 169 (1963).
9.A. P. Best and C. L. Wilson, J. Chem. Soc. 1946, 239. This was prepared by P. O. Tchir, whom we thank.
10.It was difficult to obtain the fast‐frozen cubic form of cyclohexane with a completely degassed sample. Experiments with nitrogen‐ or oxygen‐saturated samples indicated that perturbation effects were not responsible for changes in τ. But it does appear that their presence makes more probable the “freezing in” of a disordered phase. A similar effect was noted for methylcyclohexane samples. If rigorously degassed, these samples tended to crystallize instead of forming a glass on fast freezing.
11.The fraction of cubic lattice “frozen in” for a sample quickly frozen to 77 °K was determined with the DTA. This was programmed for a controlled temperature rise. The size of the exotherm (at ), which corresponded to “frozen‐in” cubic lattice annealing to monoclinic, indicated the relative amount of each lattice present at 77 °K.
12.It should be noted that the size of the sample used in this work was larger than that of Spangler and Sponer (Ref. 8). Thus our fast freezing was probably somewhat slower than theirs. The weak emission resulting from very thin samples, as used by those authors, made lifetime measurements impracticable however.
13.G. F. Hatch and G. C. Nieman, “Triplet‐Triplet Annihilation and Delayed Fluorescence in Isotopic Mixed Crystals of Benzene,” J. Chem. Phys. (to be published).
14.H. Sponer, Y. Kanda, and L. A. Blackwell, Spectrochim. Acta 16, 1135 (1960).
15.The system of notation followed here is that given in E. B. Wilson, Jr., J. C. Decius, and P. C. Cross, Molecular Vibrations (McGraw‐Hill Book Co., New York, 1955), Chap. 10.
16.For at least H6 and D1, the larger number of multiplet members is likely due to combinations, as a result of Fermi resonance interaction. This is absent in D6 because of the changes in the frequencies of and No attempt has been made to assign the multiplets of the deuterobenzenes.
17.The spectra of the slow‐cooled samples were easier to obtain, these samples being easier to prepare, as indicated by the DTA experiments. The quickly cooled samples gave less intense emission and their multiplets could not be obtained when a sample was frozen, warmed, and then quickly refrozen. This corresponded exactly to the DTA observations, where it was seen that no cubic lattice could be “frozen in” under similar circumstances. The correspondence of the DTA results with the appearance of the multiplets further supports the conclusions of Spangler and Sponer regarding the influence of different environmental sites on the spectra.8
18.E. V. Shpolskii, Usp. Fiz. Nauk 80, 255 (1963)
18.[E. V. Shpolskii, Sov. Phys.‐Usp. 6, 411 (1963)], and references therein.
19.M. V. Alfimov, N. Y. Buben, A. I. Pristupa, and V. N. Shamshev, Opt. i Spektroskopiya 20, 424 (1966)
19.[M. V. Alfimov, N. Y. Buben, A. I. Pristupa, and V. N. Shamshev, Opt. Spectry. 20, 232 (1966)].
20.It should be noted that this good agreement indicates that in this system, as was assumed. Expansion of the exponential function of Eq. (1) shows that, for small t, Eq. (3) would become If γ were even 5% of this would have been detected. In fact approaches very closely 1.00 for short times, clearly showing γ to be negligible.
21.The long straight tail of the decay curve fixes without ambiguity. Moreover, the first part of the decay curve, obtained by subtraction, yields an exponential decay whose slope is constant and is independent of the (often widely varying) curvature of the system. Attempts at constructing and subsequently analyzing curves resulting from three first‐order processes have been make for parameters of the size found here. Although such curves can often be successfully analyzed in terms of two rates for a given curvature (illumination time), so determined varies with curvature, unlike the experimental However, we hesitate to conclude that only two sites exist solely on the basis of the curvature analysis.
22.G. W. Robinson, J. Mol. Spectry. 6, 58 (1961).
23.G. W. Robinson and R. P. Frosch, J. Chem. Phys. 37, 1962 (1962);
23.G. W. Robinson and R. P. Frosch, 38, 1187 (1963)., J. Chem. Phys.
24.W. Siebrand, J. Chem. Phys. 47, 2411 (1967).
25.T. E. Martin and A. H. Kalantar, J. Chem. Phys. 49, 235 (1968).
26.G. C. Nieman (private communication).
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