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Effect of Added Quenchers in Organic Scintillator Solutions: Aromatic Halides
1.(a) M. Furst and H. P. Kallmann, Phys. Rev. 85, 816 (1952);
1.(b) M. Burton, P. J. Berry, and S. Lipsky, J. Chim. Phys. 52, 657 (1955).
2.S. Lipsky and M. Burton, J. Chem. Phys. 31, 1221 (1959).
3.H. Dreeskamp and M. Burton, Z. Elektrochem. 64, 165 (1960).
4.M. Burton, J. L. Magee, and A. H. Samuel, J. Chem. Phys. 20, 760 (1952);
4.J. L. Magee and A. H. Samuel, J. Chem. Phys. 21, 1080 (1953)., J. Chem. Phys.
5.M. Burton, Strahlentherapie (to be published).
6.M. Burton, A. K. Ghosh, and J. Yguerabide, Radiation Research Suppl. 2, 462 (1960).
7.M. Burton, paper presented before the Fourth Japan Conference on Radioisotopes, October 1961 (to be published);
7.cf. U. Fano, Comparative Effects of Radiation, edited by M. Burton, J. S. Kirby‐Smith, and J. L. Magee (John Wiley & Sons, Inc., New York, 1960), Chap. II.
8.H. P. Kallmann, M. Furst, and F. H. Brown, IRE Trans. Nuclear Sci. NS‐3, No. 6, 51 (1956).
9.The expression for is given for aerated solution. In absence of oxygen the terms involving reduce to zero.
10.In this expression is used instead of the term obtained in the straightforward derivation, because has numerical values not greatly different from unity and that of [D] is of the order of
11.This statement does not apply to 9, 10‐dibromoanthracene (DBA).
12.(a) E. J. Bowen, A. W. Barnes, and P. Halliday, Trans. Faraday Soc. 43, 27 (1947);
12.(b) E. J. Bowen and J. Sahu, J. Phys. Chem. 63, 4 (1959).
13.However, in cases where the scintillator can be excited by uv light (without excitation of the solvent) Eq. 8 reduces to and can be separately determined.
14.A word of caution is desirable. A plot of the form of curve 3 can be automatically obtained if luminescence attributable to solvent background (e.g., Cerenkov radiation) is not subtracted out. A curve like 3 must relate only to luminescence of the solute if it is to be useful for this analysis.
15.A variety of organic bromides acting directly upon fluorescent solutes, have similar quenching efficiency (reference 12a). Thus, the assumption appears reasonable.
16.J. M. Nosworthy, J. L. Magee, and M. Burton, J. Chem. Phys. 34, 83 (1961).
17.Because of photosensitivity of iodobenzene, experiments with uv, which might have definitely established that in this case (cf. footnote 13), could not be performed.
18.Nevertheless, Kallmann, Furst, and Brown8 have found that, in systems containing quenchers similar to those used in this study, the solvent is quenched with greater efficiency than is the scintillator solute. In general, as indicated in Sec. 2.2 values tend to be low.
19.J. Q. Umberger and V. K. LaMer, J. Am. Chem. Soc. 67, 1099 (1945).
20.An alternative explanation might appear implicit in the discussion of Sec. 5.2 (and in the use of Table VII). It may be suggested that quenching which presumably involves only spin perturbation of the excited state and not excitation transfer has, in actuality, a while p for excitation transfer on a collision is always i.e., the analogy suggested in the previous paragraph is simply incorrect. This explanation is cast out on the basis of the results with DBA as quencher (cf. Table I). In this case has the extraordinarily high value of a value much higher than can be explained merely on the hypothesis that
21.T. Förster, Fluoreszenz Organischer Verbindungen (Vandenhoeck and Ruprecht, Göttingen, Germany, 1951).
22.P. J. Berry, S. Lipsky, and M. Burton, Trans. Faraday Soc. 52, 311 (1956).
23.An exception can perhaps be found to such a corollary when the diffusion constant is unusually large; cf. the case of oxygen quenching, W. R. Ware, J. Phys. Chem. 66, 455 (1962).
24.M. Furst and H. P. Kallmann, Phys. Rev. 94, 503 (1954).
25.Energy transfer from quencher back to solvent would give the same result [S. Okamura, T. Manabe, and T. Motoyama, Radiation and Isotopes 1, 95 (1958)] but spectral considerations seem to rule out this alternative explanation in this case.
26.The reactions and can be substituted for reactions 0, 14, and 15 without any effect on the kinetic interpretation following.
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