Single-photon time-correlation lifetime technique

Non-steady state method13" The quenching experiments have also been carried out from measurements of lifetime by single photon time correlation technique. 

Fig. 11.5 Measurement of lifetime of anthracene in solution by single photon time correlation technique. Fluorescence decay curve of 8 X10-4 M anthracene in cyclohexane in the absence (A) and presence (B) of 0.41 M CC14. Points experimental data Line best fitting single exponential decay convoluted with instrumental response function (C) Time scale 0.322 nsec per channel. (Ref. 13).

Cline-Love L J and Shaver L A 1976 Time correlated single photon technique fluorescence lifetime measurements Anal. Chem. 48 370A-371A... 

The technique of time-correlated single-photon counting (Figure 3.4) is used to measure an excited singlet-state lifetime, x. The sample is irradiated with a very short-duration light pulse ( lns) to ensure any given molecule will only be excited once during the pulse. As soon as... 

Three techniques are actually available for measuring the fluorescence lifetime Strobe, Time Correlated Single Photon Counting (TCSPC), and multifrequency and crosscorrelation spectroscopy. Strobe and TCSPC are based on measurement in the time domain, while multifrequency and cross-correlation spectroscopy measure fluorescence lifetimes in the frequency domain. The time domain allows direct observation of fluorescence decay, while the frequency domain is a more indirect approach in which the information regarding the fluorescence decay is implicit. 

Time correlated single photon counting is a well-established technique that has been used to measure fluorescence lifetimes since the mid-1960 s. These early experiments, which used a variety of flashlamps and gaseous gap-discharge arcs as the excitation source, were reviewed by Ware [47, 48] in 1971. The traditional light sources have been replaced by laser sources in recent experiments, thus markedly extending the range of applications of this technique. Particularly well suited excitation sources for this method are the mode-locked lasers and synchronously pumped dye lasers which are capable of operation at MHz repetition rates. 

Halpern and Ware (97) have measured the fluorescence lifetimes (if) of HFA using the time-correlated single photon counting technique over a wide pressure range (0.1-700 torr) from... 

There are numerous spectroscopic studies of the chromophores bound to the chemically modified silica gel(2-4) but dynamic studies such as fluorescence lifetime measurements are rather limited. In their recent work, Lochmuller and Hunnicutt (5) have employed the time-correlated single photon counting technique and analyzed the non-exponential decays in detail to disclose the complex features of the interfaces through (10-(3-pyrenyl)decyl)dimethylmonochlorosilane chemically bonded to silica as a probe. Unfortunately, however, their method, though sophisticated enough to monitor heterogeneous fluorescence decays, cannot distinguish one microparticle from the other and hence unavoidably follows overall decays. 

Fluorescence decay curves for the pyrenyl emissions were obtained by a time - correlated single photon counting technique. The monoexponentlallty of these curves in both solvent phases is consistent with k4 k3 (l.e., that adiabatic exciplex formation is unlmportant(31)) and allows the decay constants to be equated to the excited state lifetimes. The rate constant for exciplex formation, k3, could be obtained uniquely from Eqn. 23 by assuming that kj+k2 is the Inverse of the fluorescence lifetime of 1 -ethylpyrene (EZ) i 1L- From Arrhenius and Eyring... 

Spectroscopic techniques based on the optical microscope are being used with increasing success in photophysics. Microscopic fluorescence decay measurements have been made on both thin liquid films and droplets of concentrated dye solutions.Illustrative data are given for rhodamine B in 20 pm films. A luminescence lifetime microscope spectrometer based on time-correlated single photon counting with an avalanche diode detector has measured... 

The complexes of 2,3 (sodium salt) and 4 (potassium salt) with P-CD and (2,3,6- tri-0-methyl)-/ -CD were studi using steady-state fluorescence and time-correlated, single-photon counting techniques [52]. The formation of both 1 1 and 2 1 complexes between p-CD and 2,3 was confirmed. Trimethyl- -CD gave evidence only of 1 1 complexes. The fluorescence decay of systems giving exclusively 1 1 complexes was collected at CD concentrations that ensure more than 90% complexation. The analysis performed using a continuous lifetime distribution model... 

Spectroscopy of single molecules is based on fluorescence correlation, photoncounting histograms, or burst-integrated-lifetime techniques. Each case requires recording not only the times of the photons in the laser period, but also their absolute time. Modem time-resolved single molecule techniques therefore use almost exclusively the FIFO (time-tag) mode of TCSPC. The FIFO mode records all information about each individual photon, i.e. the time in the laser pulse sequence (micro time), the time from the start of the experiment (macro time), and the number of the detector that detected the photon (see Sect. 3.6, page 43). 

Another luminescence-based method is luminescence lifetime measmement in which the decay of the excited states with time is followed [38]. Liuninescence lifetime is the time required for the intensity to decrease to 1 /e of its initial value. The most common technique is time-correlated single photon coimting which uses a pulsed light somce, one monochromator for the excitation and one for the emission side, a PMT with fast response as the detector, a time-to-amplitude converter and data storage in a multichaimel analyzer. 

Luminescence lifetimes measured using pulsed laser excitation involve either direct detection of emission decays with time or a technique known as time-correlated single photon counting (TCSPC). The latter technique involves repeated measurement of the delay time between the excitation pulse and the arrival of an emitted photon packet above a given discrimination level the intensity-time decay profile accumulates over many millions of excitation pulses. The TCSPC experiment has the advantage that much better signal to noise can be obtained relative to the direct capture of the luminescence decay. 

Time-correlated single-photon counting techniques for determining the lifetime of short-lived excited states. 

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