This potential produces a saddle point in the centre of the trap, which traps ions along the axial direction.
en.wikipedia.org Here, we have substituted the integration region by because both contain the origin, which is a saddle point, hence they are equal up to an exponentially small term.
en.wikipedia.org The saddle point represents the highest energy point lying on the reaction coordinate connecting the reactant and product; this is known as the transition state.
en.wikipedia.org In contrast, the sandwich configuration maximizes overlap of the pi system, is least stable, and represents an energetic saddle point.
en.wikipedia.org If the function is smooth, or, at least twice continuously differentiable, a critical point may be either a local maximum, a local minimum or a saddle point.
en.wikipedia.org