Resonance excitation in a quadrupole ion trap: modification of competing dissociative channel yields

Abstract

The molecular ion ( m/z 134) of n-butylbenzene, mass-selected in a quadrupole ion trap, has been employed in an investigation of the influences on ion internal energy of the excitation conditions, trapping parameter q z , and collisional cooling periods before a period of resonance excitation. A cooling period following ion isolation and prior to resonance excitation brings about marked reductions in both ion kinetic energy, related to an internal energy decrease effect with a short cooling period, and ion spatial distribution within the ion trap as a result of momentum-exchange collisions with helium. However, as the cooling time is prolonged, an internal energy increase of the precursor ion is observed: the parent ions attain a greater degree of internal energy during the resonance excitation period. Concurrent with the thermalization of ion kinetic energy, ion activation is observed by increasing the number of collisions during a cooling delay.