THE TIME‐RESOLVED PHOTON‐COUNTING FLUOROMETER AT THE NATIONAL SYNCHROTRON LIGHT.SOURCE

A single‐photon‐counting fluorometer, capable of steady‐state and time‐dependent measure‐ments, is now operational at port U9B of the National Synchrotron Light Source at Brookhaven National Laboratory. Excitation wavelengths are selected by a prism‐grating double monochromator. Emission energies are chosen by filter(s) or by a one‐meter Spex monochromator. Commercial electronics are used for data acquisition, except for special circuitry required by the high (53 MHz) repetition rate of the synchrotron. A large sample chamber allows flexibility in arranging optical components and samples. The standard optical configuration of the sample chamber consists of a focusing mirror, a six position excitation optic wheel, a turntable with four thermostatted cuvette holders, a six position emission optic wheel, and an f/0.7 emission collection lens. Data acquisition and the setting of correct wavelengths and sample chamber optics are controlled by a Tektronix 4052 computer via the IEEE‐488 General Purpose Interface Bus. Time‐dependent fluorescence data are transferred to a VAX 11/730 for analysis; current deconvolution software includes nonlinear least‐squares programs for single curve and global analysis.