Film phosphorescence spectra from

Fig. 15. (A) Absorption, fluorescence and phosphorescence spectra of BChl a in vitro at 77 K spectra scaled for convenient presentation also note break of horizontal scale (B) Phosphorescence spectrum of quinone-depleted (-Q) and quinone-containing (+Q) Rb. sphaeroides reaction centers in polyvinyl-alcohol film at 22 K (C) Energy diagram for the components involved in triplet-triplet energy transfer with carotenoids. (A) and (B) and numerical values for the triplet-state energies of BChls a and b and the primary-donors of Rb. sphaeroides and Rp. viridis, i.e., [BChl a and [BChl bjj, respectively, are taken from Takiff and Boxer (1987) Phosphorescence spectra ofbacteriochlorophylls. J Am Chem Soc 110 4425.

Figure 8 is the phosphorescence spectrum taken from a glassy solution of poly(n-propyl methyl silylene) in methyl cyclopentane at 89°K. This emission is similar in width to the film emission, as are the solution spectra of the other polymers. Again delayed fluorescence is evident but the sharp vibrational fine structure is lost. The solution and film spectra are not expected to be comparable since they represent conformational equilibria (at room temperature for film and the Tg of 3-methylpentane for the solutions). 

We have examined the emission spectra of a variety of polysilylenes as thin films and solutions. The solution fluorescence ther-mochromism provides evidence to support the rotational isomeric state model used to interpret the absorption spectrum. The structured character and low yield of phosphorescence in the alkyl polysilylenes suggest that the triplet is the immediate precursor to photochemical scission. The change in character of both fluorescence and phosphorescence on progressing from phenyl to naphthyl in the aryl series indicates that the transitions in the naphthyl polymers are principally ir—it. ... 

Fig. 3.26 Absorption and delayed emission spectra of PF2/6 in MTHF at 80 K (upper half). The emission spectrum was taken 5 ms after optical excitation at 3.05 eV DF corresponds to delayed fluorescence and Ph to phosphorescence. Absorption and delayed emission of a PF2/6 film at 80 K (lower half). The delay was 5 ms after excitation at 3.05 eV Reprinted from [142], copyright 2002, with permission from the American Institute of Physics.

Polymer Luminescence Spectra. Figure 1 shows typical fluorescence and phosphorescence excitation and emission spectra obtained from commercial polypropylene film (or powder). Poly(4-methylpent-l-ene) exhibits similar spectra to those of polypropylene. The excitation spectrum for the fluorescence has two distinct maxima at 230 and 285 nm while that of the phosphorescence has only one distinct maximum at 270 nm with rather weak and diffuse structure above 300 nm. It is clear from these results that the fluorescent and phosphorescent chromophoric species cannot be the same. This, of course, does not rule out the fact that both may arise from carbonyl emitting species, as will be shown later, since these chromophoric groups when linked to ethylenic unsaturation can have quite distinct absorption (14) and emission spectra (15,16,17). 

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