The microscopic reaction mechanism of diphenyl ether with nitrous acid in the presence or absence of O₂ was studied by laser flash photolysis. The main characteristic peaks in these transient absorption spectra were attributed and the decay trends were investigated. The final photolysis products were analyzed by using GC-MS method. OH radical obtained by nitrous acid exposed to 355 nm laser beam reacts with diphenyl ether to produce C₁₂H₁₀O-OH adduct. In the absence of O₂ the decay constant of C₁₂H₁₀O-OH adduct was measured to be (1.86±0.14)×10⁵ s^－1 and the final photolysis products were phenol, o-hydroxydiphenyl ether, p-hydroxydiphenyl ether and p-nitrodiphenyl ether. While in the presence of O₂ the decay constant of C₁₂H₁₀O-OH adduct was measured to be (6.6±0.4)×10⁶ s^－1.

Key words: laser flash photolysis, diphenyl ether, transient absorption spectrum