The Perkin Elmer LS 55 luminescence spectrometer is a very versatile instrument that allows measurement of fluorescence, phosphorescence, and chemiluminescence or bioluminescence of a liquid, solid, powder, or thin film sample. The instrument is simple to operate and is controlled by easy-to-use software. The sample is illuminated in the wavelength range of 200 to 800 nm and the emission spectra recorded from 200 to 900 nm. Excitation and emission monochromators can be independently or synchronously scanned, while the Prescan mode is ideal for method development and locating of peak excitation and emission maxima. The Model LS 55 Series uses a pulsed Xenon lamp as a source of excitation. Fluorescence data are collected at the instant of the flash while phosphorescence data are collected in the dark period between each flash. The use of the pulsed Xenon lamp obviates the need for a mechanical means of chopping the excitation and emission beams, thus leading to improved precision and speed of analysis. The instrument software includes application programs for observing short (msec) and long (seconds) phosphorescence decay curves in addition to spectra.