Multiexponential analysis

Photophysics of NDI-650 and NDI-2000 polyurethane Films. The fluorescence spectrum of an NDI-650 polyurethane film ( e t = 300 nm) is dominated by excimer anission (Figure 11). A preliminary multiexponential analysis of the excimer and monomer emission decay curves indicates a complicated photophysical system. However, it can be reported that the long-lived component of the excimer decay curve (taken at 500 nm) does yield a lifetime of 22 ns for excimer emission, close to that obtained in CH2CI2. 

Table IV. Multiexponential Analysis of L. Dorsi (Heifer) Muscle Muscle State No. of Processes Amplitude 96 T (m.sec.)...

Tabic 63. Multiexponential Analysis of tiie Intensi Decays of Vr Base in Benzene-Methanol MxtureS ... 

The MEM analysis of time-resolved fluorescence decays of several copolymers is shown in Fig. 15.18a. For the homopolymer PF2/6, only a narrow distribution is observed around 360 ps. However, for copolymers PF/FLx, with different fractions of fluorenone residues, distributed randomly along the polymer chain, the distribution at 360 ps is accompanied by two additional peaks. These are observed around 20 and 100 ps as a result of quenching of polyfluorene emission, due to energy transfer from the fluorene to the fluorenone sinks. Figure 15.18b shows the fluorescence decay of the copolymer labelled with 25 % of fluorenone groups, analysed with a sum of three exponential functions. Note the good agreement between MEM and multiexponential analysis [91]. 

In contrast, in the above-described equivalent circuit analysis, we first separated the individual components by physical means, using various reconstitution methods. Contrary to common impressions, our data of isolated components was subjected to multiexponential analysis to obtain the time constants, such as X3 and X[. These deconvoluted data are then tested with the equivalent circuit. The equivalent circuit imposes a constraint that the investigator cannot manipulate or overcome by "massaging the data. Equation 128.3 can be simplified by using a brief light pulse so that p(t) = 8(t), where 8(t) is... 

For a pure, isolated photoelectric current component. Equation 128.9 must be satisfied. Taken together. Equation 128.8 and Equation 128.9 satisfy the zero time-integral condition (Equation 128.1). It is, therefore, not surprising that the definition of capacitative current provides the crucial constraint. It is also not surprising that the conventional multiexponential analysis is so misleading in membrane-phase photochemistry, capacitative events are a major feature of interfacial photochemistry. 

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