Limitations of the effective potential for the evaluation of the ion energy in the RF-driven quadrupole field

The concept of the effective potential provides inadequate estimation of the ion energy in RF-driven quadrupole fields. It is especially limited for the quantitation of additional enthalpy introduced by the RF-driven field for an ion molecule reaction. On the contrary, the effective potential is clearly successful in describing of the ion oscillation frequency, and has been surprisingly powerful considering the strict limitations of the adiabatic approximation. This work is an attempt to understand this contradiction and to consider a novel concept of the estimation of the ion energy in an RF field. This theoretical model for the averaged ion energy is useful in describing specific features of the RF field contribution to the enthalpy of ion molecule reactions. To demonstrate this effect, several ion molecule reactions are investigated experimentally including cluster formation, endothermic and exothermic oxidation reactions. (c) 2005 Elsevier B.V. All rights reserved.