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31
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13444289080
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Based on measured radiative rate constants of the order of 106 −10 7 s −1 for a variety of fluorescent saturated hydrocarbons (Ref. 28) a fluorescence quantum yield of less than 5×10 −6 would imply a lifetime of excited isooctane of less than 5 ps. Also, picosecond transient absorption spectroscopy with excitation above the ionization threshold have indicated no evidence for a state of iso-octane of lifetime longer than 10 ps
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(1986)
Chem. Phys. Lett
, vol.126
, pp. 219
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Miyasaka, H.1
Mataga, N.2
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33
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0029322845
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The origin of this discrepancy is unknown, but recent measurements that we have made of the emission of benzene from solutions of isooctane excited in the iso-octane absorption system from 150 to 160 nm, provide a sensitization yield of only 0.02 at 1.0 M benzene, implying an iso-octane lifetime of less than 6 ps. Accordingly, at 0.1 M hexafluorobenzene, we expect negligible (<0.2%) sensitization of hexafluorobenzene by excited iso-octane
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(1995)
J. Phys. Chem
, vol.99
, pp. 10471
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Saik, V.O.1
Lipsky, S.2
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34
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85086293804
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Ph.D. thesis, University of Minnesota
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(1984)
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Lyke, R.1
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37
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85086293453
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These considerations have been previously invoked to simplify the analysis of the concentration dependence of the fluorescence of hexafluorobenzene in similar solvents excited with beta particles (Ref. 30)
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48
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85086295323
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The tracer diffusion constant of [formula omitted] in cyclohexane at 25 °C is [formula omitted] (Ref. 41). This was scaled to [formula omitted] in iso-octane using the ratio of the viscosity of cyclohexane at 25 °C of 0.898 cp to that of iso-octane at [formula omitted] of [formula omitted] cp (extrapolated from higher temperature measurements via the equation [formula omitted] (Ref. 42). The self-diffusion constant of iso-octane, [formula omitted] at [formula omitted] was obtained via the semiempirical equation of Dullien [i.e., [formula omitted] where η is the viscosity, [formula omitted] the molar volume, [formula omitted] the critical volume, and all units are cgs] (Ref. 43) which predicts the self-diffusion constants of 32 liquids with an average deviation of [formula omitted] Using [formula omitted] cp at [formula omitted] (Ref. 42), [formula omitted] (interpolated for [formula omitted] (Ref. 42) and [formula omitted] gives [formula omitted] Adding this to the tracer diffusion constant of [formula omitted] provides us with the value [formula omitted] in normal iso-octane. No isotope correction was attempted. The Onsager radius of 321 Å at [formula omitted] in iso-octane was obtained using a NaD optical dielectric constant of [formula omitted]
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55
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85086293702
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These values of [formula omitted] are obtained using the reported value of γ at [formula omitted] (Ref 46) and the value [formula omitted] for iso-octane at [formula omitted] (Ref 40). The assumption we made is that γ is not strongly dependent on temperature. Using the 20°C value for [formula omitted] of 288 nm, gives values of [formula omitted] 11% higher
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56
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85086295603
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Bottcher and Schmidt (Ref. 49) have suggested that the average range of electrons photoejected from saturated hydrocarbon liquids at energies [formula omitted] above threshold and those similarly ejected from TMPD in the same solvents should not significantly differ. The approximate agreement in the values of [formula omitted] of 17.5 for photoejection from neat isooctane containing [formula omitted] and of 16.5 from TMPD in iso-octane containing [formula omitted] tends to further support this view. Additionally, it would suggest that the value of [formula omitted] for TMPD in iso-octane without scavenger (Ref. 46) should be close to that of neat iso-octane and, therefore, that the value of [formula omitted] obtained by Casanovas et al., (Ref. 2) may be too low
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