Time- and space-correlated single-photon-counting spectroscopy

Simultaneous acquisition of time- and space-information in time-domain single photon counting spectroscopy became feasible by a recent advance in microchannel-plate photomultiplier-tube technology: we present a novel MCP-PMT detector, featuring a space- sensitive delay-line anode. The detector is characterized by temporal and spatial instrument response functions of 75 ps and 100 micrometer FWHM, respectively, at 200 space channels and a dynamic range of 105. By employing a two-dimensional multichannel analyzer with transputer, 70.000 cps through-put or higher is possible. No photons are lost at the exit slit of the monochromator, as in standard, one-channel time-correlated single photon counting spectroscopy, and sensitive biological samples can be studied at reduced excitation energies. We applied the novel detector to study the basic photophysics of DAPI and its interaction with DNA.