Multiphoton dissociation of ions derived from isopropanol and deuterated analogues in a QUISTOR with low power CW infrared laser radiation

A versatile technique employing pulsed quadrupole ion storage mass spectrometry and a low power CW CO2 laser for the study of slow infrared multiphoton dissociation of gaseous ions under collision-free conditions is described. Multiphoton dissociation of gaseous ions derived from isopropanol. 2-d1-isopropanol, isopropan-d-ol and perdeutcroisopropanol, with irradiation for up to 110 ms with intensities of ~20 W cm−2, was effected. Irradiation of proton (or D+) bound alcohol dimers showed that three dissociative reaction channels are utilized in multiphoton dissociation: the photodissociation yield for the dissociative reaction channel of lowest activation energy increases and becomes dominant with collisional and radiative relaxation of the ions. Of the three ionic photoproducts of multiphoton dissociation of proton bound alcohol dimers, only the protonated ether is found to be photodissociative under the prevailing conditions. The photochemical stability of the ion formed by loss of the elements of propene from the proton bound alcohol dimer contrasts sharply with the multiphoton dissociation of the proton bound alcohol–water mixed dimer, and serves to demonstrate the applicability of multiphoton dissociation to distinguish between gaseous ion isomers.