Ion optical design of a collinear laser-negative ion beam apparatus

Abstract

An apparatus for photodetachment studies on atomic and molecular negative ions of medium up to heavy mass (M ≃ 500) has been designed and constructed. Laser and ion beams are merged in the apparatus in a collinear geometry and atoms, neutral molecules and negative ions are detected in the forward direction. The ion optical design and the components used to optimize the mass resolution and the transmission through the extended field-free interaction region are described. A 90° sector field magnet with 50 cm bending radius in combination with two slits is used for mass dispersion providing a resolution of M∕ΔM≅800 for molecular ions and M∕ΔM≅400 for atomic ions. The difference in mass resolution for atomic and molecular ions is attributed to different energy distributions of the sputtered ions. With 1 mm slits, transmission from the source through the interaction region to the final ion detector was determined to be about 0.14%.

Experimental studies of partial photodetachment cross sections in K−below the K(7 2P) threshold

“…The ion current through the interaction region was typically on the order of 1 nA. The apparatus was recently upgraded to improve the mass resolution and the transmission through the interaction region, as described in detail by Diehl et al [22]. The sector magnet was only single focusing; therefore, two single-focusing Einzel lenses were used in order to achieve a symmetric beam and improve the transmission through the system.…”

Light induced suppression of sulfur in a cesium sputter ion source

“…2 was about 10 nA. However, the transmission of the ion beam apparatus at GUNILLA is only 0.1% [14]. Thus, the estimated total Cl − current emitted from the source was of the order of 10 μA, i.e.…”

Anion formation by neutral resonant ionization

“…Certainly, 5 mm £ sample holes will behave as if the sample is flat with the surface because the electron promotion of excited states will be too weak. Some of the measurements were made at GUNILLA and report sample pitting that leads to excited states of Cs in the pits [45]. Considering the 1.5 and 2 mm diameter plots in Fig.…”