Efficient magnetic focusing of low-energy ions (1–5 eV) onto solids for use in surface chemistry studies

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Abstract
A method is described that allows the efficient collection and focusing of ions, with kinetic energies between 1 and 5 eV, onto a nonmagnetic metal surface. Magnetic fields near the sample are used to focus the low-energy ions and typical currents achieved thus far exceed 100 nA/cm2 for 1-eV ion energies. The magnetic field of a magnet placed behind the sample significantly reduces the problem of transverse displacement of the ions due to beam divergence and space-charge effects. The magnetic field confines the particle to a circular orbit along the axial direction (cyclotron motion), while leaving the kinetic energy of the ion unaffected. We have utilized this method to interact Ar+ and CH+3 with 1-eV translational energy and 100 nA of current on a Pt surface.