Dissociation rates of energy-selected benzene cations: comparison of experimental results from ion cyclotron resonance and cylindrical ion trap time-of-flight mass spectrometry

Millisecond decay rates of the perdeuterio benzene cation (C6D6+) are measu red in two different ion storage equipments. Resonance-enhanced two photon ionization with a single laser beam leads to the production of the perdeute rio benzene cations without internal energy. By absorption of a third photo n from the same laser or a second laser beam the ions are excited to intern al energies of 4.64 eV and the decay rate is measured by the time dependent appearance of the C6D5+ and C6D4+ fragment within the electro-magnetic tra p (Penning trap) of an ion cyclotron resonance (ICR) mass spectrometer and an electrodynamical ion trap (Paul trap) incorporated in a reflectron time- of-flight mass spectrometer. After correction for infrared relaxation we ob tain a unimolecular decay rate constant of 1.15 x 10(3) s(-1). We perform R RKM calculations for this experimental result and for previous values achie ved from decay rate measurements in a reflectron mass spectrometer. They ar e in good agreement with the experimental dependence of decay rate constant s for benzene (C6H6+) and perdeuterio benzene cations (C6D6+) over a wide r ange of decay rate constants between 10(3) and 2 x 10(6) s(-1). (C) 1999 El sevier Science B.V.