No abstract

The maximum entropy method and a new more robust exponential series method are described and tested for the recovery of underlying fluorescence lifetime distributions derived from digital fluorescence data. Both real and simulated data are used in this study. Except for the resolution of single-lifetime systems, it is found that the two methods are similar in their resolving powers. The problem of differentiating between the case of a continuous distribution and three discrete components is discussed. The effects of radio-frequency noise, background subtraction, time base, and data precision on the recovery of distributions are described.

13) Note the value reported in ref 14 was not corrected for the error reported by Allendoerfer (ref 15). All other g values reported therein were so corrected.

No abstract

This work describes a stroboscopic optical boxcar technique for the determination of fluorescence lifetimes which achieves performance comparable to techniques such as time-correlated single photon counting or phase modulation. The stroboscopic technique is based on the use of a traveling wave injected into a delay line connecting the dynodes of a photomultiplier tube. The transient potential difference created between two adjacent dynodes results simultaneously in significant amplification and the generation of a ‘‘gate’’ for the amplification process. Accurate control of the timing between the flashing of the gated lamp and the computer controlled delayable triggering of the photomultiplier tube pulser allows the gate to be placed at any time position within the range of the digital delay generator. The intensity of the fluorescence emission can thus be measured as a function of time relative to the excitation flash yielding data which is very similar to that from time-correlated single photon counting. Data analysis is done by iterative reconvolution in a procedure very similar to the analysis of time-correlated single photon counting data. Fluorescence lifetimes from a few hundred picoseconds to hundreds of nanoseconds can be determined to an accuracy and precision of better than ±2%.