A study was made of the induced absorption in amorphous selenium parti
cles (average radius approximately 20 nm) embedded in a polymer. A pic
osecond pump and probe technique was used. The change in the absorptio
n was measured in the spectral range 550-750 nm when the pump radiatio
n was in the form of pulses of 15 ps duration and 2.3 eV photon energy
. The induced-absorption spectra were attributed to optical exciton-bi
exciton transitions. The exciton lifetime was estimated to be 424 +/-
32 ps.