Laser flash photolysis studies were carried out on two types of silver nanoparticles prepared byγ-radiolysis of Ag⁺ solutions in the presence of polyphosphate as the stabiliser. Type I silver nanoparticles displayed a surface plasmon band at 390 nm. Type II silver nanoparticles showed a 390 nm surface plasmon band with a shoulder at 550 nm. On photoexcitation in the surface plasmon band region, using 35 picosecond laser pulses at 355 nm and 532 nm, the type II solutions showed transient bleaching and absorption signals in the 450–900 nm region, which did not decay appreciably up to 5 nanoseconds. These transient changes were found to get annealed in the intervalt where 5 ns<t< 100 ns. Extended photolysis of the nanoparticle solutions with repetitive laser pulses resulted in a decrease in the values of the average particle size which were measured by employing the dynamic light scattering technique.