Time correlated single photon counting

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Under time-correlated single photon counting ( English time-correlated single photon counting , TCSPC ) refers to a technique for the measurement of rapidly changing in time ( picosecond ) light intensities . The main application is the measurement of the fluorescence lifetime , and based on it techniques such as fluorescence lifetime microscopy (engl. Fluorescence lifetime imaging microscopy , FLIM). But it is also possible to analyze the temporal behavior of pulsed or modulated light sources, right up to the characterization of circulating electron bunches in storage rings of synchrotrons on the basis of the synchrotron radiation emitted .

Schematic representation of the development of a TCSPC histogram during the measurement of a fluorophore with a mono-exponential fluorescence lifetime (excitation pulse hits the fluorophore at approx. 4 ns; above: logarithmic representation )

To measure the fluorescence lifetime , the fluorophores to be examined are excited by means of a pulsed light source (e.g. laser or flash tube ) . The time measurement is started by the excitation pulse and the photon emitted during the transition from the excited state to the ground state stops the measurement. The measurement is repeated many times and the individual temporally correlated photons (in relation to the excitation pulse) are sorted into a so-called TCSPC histogram according to their measured time . This typically has a temporal channel resolution or class width of approx. 1 to 50 ps and reflects the exponential decrease in the fluorescence intensity after the excitation.

The fluorescence lifetime depending on the measurement technique in the time domain (engl. Time domain ) or in the frequency domain (engl. Frequency domain ) are determined, wherein the time-correlated single photon counting is the most commonly used method in the time domain.

See also

literature

  • Desmond V. O'Connor, David Phillips: Time-Correlated Single Photon Counting. Academic Press, London / Orlando 1984, ISBN 978-0125241403 .
  • W. Becker: Advanced Time-Correlated Single Photon Counting Techniques. Springer, Berlin 2005, ISBN 978-3540260479 .
  • Joseph R. Lakowicz : Principles of Fluorescence Spectroscopy. 3rd edition, Springer, Berlin 2006, ISBN 978-0387312781 .

Web links

Individual evidence

  1. ↑ Holldack K., v. Hartrott M., Hoeft F., Neitzke O., Bauch A., Wahl M .: Bunch Fill Pattern at BESSY monitored by Time-Correlated Single Photon Counting. In: Proc. SPIE. Vol. 6771 (2007).