Single-photon timing

Volkmer, A., Hatrick, D. A. and Birch, D. J. S. (1997). Time-resolved nonlinear fluorescence spectroscopy using femtosecond multiphoton excitation and single-photon timing detection. Meas. Sci. Technol. 8, 1339 19. 

Fig. 6.7. Schematic diagram of a single-photon timing fluorometer.

Lifetime instruments using a streak camera as a detector provide a better time resolution than those based on the single-photon timing technique. However, streak cameras are quite expensive. In a streak camera, the photoelectrons emitted... 

When the number of data points is large (i.e. in the single-photon timing technique, or in phase fluorometry when using a large number of modulation frequencies), the autocorrelation function of the residuals, defined as... 

The principle of the determination of time-resolved fluorescence spectra is described in Section 6.2.8. For solvent relaxation in the nanosecond time range, the single-photon timing technique can be used. The first investigation using this technique was reported by Ware and coworkers (1971). Figure 7.3 shows the reconstructed spectra of 4-aminophthalimide (4-AP) at various times after excitation. 

Chapter 6 described the current techniques employed in time-resolved fluorescence spectrocopy. The time resolution of these techniques ranges from a few picoseconds (streak cameras) to a few hundreds of picoseconds (single-photon timing with flash lamp excitation). The time resolution can be greatly improved by using the fluorescence up-conversion technique. 

Discrimination of species in complex samples can be made via lifetime measurements using the single-photon timing method coupled to NSOM. 

In principle, lifetime imaging is possible by combination of the single-photon timing technique with scanning techniques. However, the long measurement time required for collecting photons at each point is problematic. 

A much better time resolution, together with space resolution, can be obtained by new imaging detectors consisting of a microchannel plate photomultiplier (MCP) in which the disk anode is replaced by a coded anode (Kemnitz, 2001). Using a Ti-sapphire laser as excitation source and the single-photon timing method of detection, the time resolution is <10 ps. The space resolution is 100 pm (250 x 250 channels). 

The background resulting from Raman and Rayleigh scattering can be drastically reduced using a pulsed laser and the single-photon timing technique (see Chapter... 

Recently the fluorescence of IR-132 has been determined using single-photon timing at detection levels down to photon bursts from single molecules in 1 picoliter of a 25 fM solution of the dye.(14) At these extremely low concentration levels solvent... 

Multianode versions of MCP-PMs(88) are now available which are particularly suitable for multiplexed single-photon timing measurements (see Sections 12.2.5 and 12.2.6). The potential for MCP-PMs for 2-D imaging has also been demonstrated using... 

Figure 12.23. Photon counting streak camera measurement of the fluorescence decay of DODCI (I0 fi Afl in water, (a) counts (b) weighted residues. Lifetime = 0.66 0.01 ns, (From Ref. 95.) Note the similarities with single-photon timing data, e.g., sec Figure 12,14. Reduced/2 = 1.37.

Phase-modulation fluorometry has been performed with APDs to a lesser extent than has single-photon timing, but nevertheless there are some reports of this combination006, 107)... 

D. J. S. Birch, K. Suhling, A. S. Holmes, A. D. Dutch and R. E. Imhof, Array fluorometry the theory of the statistical multiplexing of single-photon timing, in Time-Resolved Laser Spectroscopy in Biochemistry II, (J. R. Lakowicz, ed.), Proc. SPIE 1204, 26-34 (1990). 

D. L. Farrens and Pill-Soon Song, Subnanosecond single photon timing measurements using a pulsed diode-laser, Photochem. Photobiol. 54, 313-317 (1991). 

A. Lacaita, S. Cova and M. Ghioni, Four-hundred-picosecond single photon timing with commercially available avalanche photodiodes, Rev. Sci. Instmm. 59, 1115-1121 (1988). 

A. Lacaita, S. Cova, F. Zappa and P. A. Francese, Subnanosecond single-photon timing with commercially available germanium photodiodes, Opt. Lett. 18, 75-77 (1993). 

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).

Figure 1. Block diagram of single-photon time-correlation apparatus from Barker and Weston 11 HV, high-voltage supplies L, lamp PI, photomultiplier M, monochromator FURN, furnace C, sample cell LP, light pipe F, interference filter P2, photomultiplier AMP, amplifier DISCI, discriminator D1SC2, discriminator T-S, timer scaler DL, delay line TAC, time-to-amplitude converter BA, biased amplifier MCPHA, multichannel pulse-height analyzer TTY, teletype printer and paper-tape punch REC, strip-chart recorder.

Single photon timing See time-correlated singjte photon counting. 

Time-correlated single photon counting A technique for the measurement of the time histogram of a sequence of photons with respect to a periodic event, e.g. a flash from a repetitive nanosecond lamp or a CW operated laser mode-locked laser). The essential part is a time-to-amplitude-converter (TAG) which transforms the arrival time between a start and a stop pulse into a voltage. Sometimes called single photon timing. 

We can provide the following summary for the decay behavior of simple aliphatic aldehydes and ketones with little or no vibrational excitation energy on the Sp manifold under "isolated" molecule conditions at room temperature. A typical fluorescence decay time (tp) measured by a single-photon time-correlated lifetime apparatus (248) is 2-5 ns (42,101,102). A typical fluorescence quantum yield (ketones measured by fluorescence excitation spectroscopy is 10-, but the value is somewhat lower for aliphatic aldehydes (101,102). These values indicate that the radiative process (kp) is lO -lO s-1, three orders of magnitude slower than the total rate of nonradiative processes (kpjp) of 10 10 s-1. A typical radiative lifetime (tr) is 0.1 0.5 ps for aliphatic aldehydes and 0.1 ps for aliphatic ketones. 

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