Stepwise photoionization of 1,2-dihydroxybenzene vapor

The stepwise ionization processes of 1,2-dihydroxybenzene vapor at 315-275 and 266 nm were studied by the techniques of mass spectrometry, total ioniz ation current spectroscopy, and zero electron kinetic energy spectroscopy. A two-step ionization process yielding the molecular ion prevails at a lase r intensity up to similar to 10(7) W/cm(2). As the radiation intensity incr eases, fragmentation takes place via the dissociation of molecular and frag ment ions due to absorption of one additional photon. The formation pathway s of principal fragment ions are discussed.