Abstract—Reaction kinetics of radicals produced by the nanosecond laser flash photolysis of 2, 2′-dithiobis (pyridine N-oxide) and related compounds have been studied. The transient absorption band at 360 nm was attributed to the radical in which the unpaired electron mainly localizes on the S atom (N-oxypyridyl-2-thio radical). The reactivities of the radical for conjugated dienes are lower than those of the pyridyl-2-thio radical, suggesting that a ...