A wide-range high-accuracy phase fluorometer

A phase fluorometer is described with an acousto-optical modulator, employing modulation frequencies of 15 and 60 MHz. The instrument has an accuracy of +or-0.02 ns for lifetimes below 1 ns and of 2% for lifetimes from 1 to 100 ns. The precision for short lifetimes is +or-7 ps, for longer times +or-1%. The setup shows great versatility. Spectral selection in the fluorescent emission is possible; the instrument can be easily converted to a fluorimeter.