Synchronisation of TCSPC Modules

As briefly mentioned above, a system of two synehronised TCSPC ehannels can be used to obtain correlation data on a time scale shorter than the dead time. The required system connections are shown in Fig. 5.120. 

Micro Time Start-Stop Time Macro Time Time from start of experiment 

In principle, correlation at even shorter time-scales is possible by including the micro times of both modules in the calculation of the correlation function. The problem with this approach is that the micro time scales of the modules may be slightly different, and the macro time transitions may be shifted due to different transit times in the detectors, cables and TCSPC modules. Correcting all these effects is extremely difficult, yet not impossible. Suitable calibration and correlation algorithms were developed by S. Felekyan, R. Ktihuemuth, V. Kudryavtsev, C. Sandhagen, and C.A.M. Seidel, Universitat Dortmund. 

At a time scale between 0.1 and 1 ms the curves are dominated by the diffusion time. Intersystem crossing is apparent between land 10 ps. Below 10 ns the singlet lifetime causes the eorrelation curve to drop to one. A fit to a suitable model delivers an average number of molecules in the focal volume of 3.5, a diffusion time of 0.3 ms, an antibunehing time of 3.5 ns, a triplet lifetime of 1.9 ps, and a mean triplet population of 29%. 

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