Essential components include an excitation source (Hg lamp or laser),a means of "monochromatizing" the excitation source (filter or monochromator),a thermostatically controlled sample chamber, an emission selector (filter or monochromator), a detector (diode array, photomultiplier tube, or charge-coupled device), detection elecronics (picoammeter) or photo counter), and a readout device (strip chart recorder or computer).