An absorption maximum and a molar extinction coefficient of a transient in
the laser flash photolysis of bis(4-methoxybenzoyl) peroxide were determine
d as 900 nm and 750 M(-1)cm(-1), respectively. The comparison of products f
or the photolysis at 266 nm with and without 1064-nm pulse gave a solid evi
dence of 4-methoxybenzoyloxyl radical being responsible for the absorption.