Design and performance of a high-flux electrospray ionization source for ion soft landing
We report the design and evaluation of a new high-intensity electrospray ionization source for ion soft-landing experiments. The source incorporates a dual ion funnel, which enables operation with a higher gas load through an expanded diameter heated inlet into the additional first region of differential pumping. This capability allowed us to examine the effect of the inner diameter (ID) of the heated stainless steel inlet on the total ion current transmitted through the dual funnel interface and, more importantly, the mass-selected ion current delivered to the deposition target. The ion transmission of the dual funnel is similar to the transmission of the single funnel used in our previous soft landing studies. However, substantially higher ion currents were obtained using larger ID heated inlets and an orthogonal inlet geometry, in which the heated inlet was positioned perpendicular to the direction of ion propagation through the instrument. The highest ion currents were obtained using the orthogonal geometry and a 1.4 mm ID heated inlet. The corresponding stable deposition rate of ∼1 μg of mass-selected ions per day will facilitate future studies focused on the controlled deposition of complex molecules on substrates for studies in catalysis, energy storage, and self-assembly.