A low energy ion source for electron capture spectroscopy

Abstract

We report on the design of an ion source for the production of single and double charged Helium ions with kinetic energies in the range from 300 eV down to 5 eV. The construction is based on a commercial sputter ion gun equipped with a Wien-filter for mass/charge separation. Retardation of the ions from the ionizer potential (2 keV) takes place completely within the lens system of the sputter gun, without modification of original parts. For 15 eV He(+) ions, the design allows for beam currents up to 30 nA, limited by the space charge repulsion in the beam. For He(2 +) operation, we obtain a beam current of 320 pA at 30 eV, and 46 pA at 5 eV beam energy, respectively. In addition, operating parameters can be optimized for a significant contribution of metastable He*(+) (2s) ions.

Spin Blocking in the Correlated Double-Electron Capture from Metal Surfaces

“…Nonmetallic adsorbates lead to a strong decrease of the INS intensity at E f , as shown for adsorption of 0.1 ML of carbon. The same effect is also observed for adsorption of H 2 from the residual gas [22] and oxygen or cesium. Figure 1(b) shows the electron spectrum obtained for the single electron capture by 30 eV He Ãþ ð2sÞ ions at a 4 ML Fe film.…”

“…This correlated double capture creates preferentially a singlet two-hole final state in the metal, explaining previous results. Doubly ionized He þþ , metastable He Ãþ ð2sÞ, and He þ ions were created using a modified sputter gun [22]. In order to avoid molecular hydrogen ions in the beam, the 3 He isotope was used.…”

Hole doping effect of MoS2 via electron capture of He+ ion irradiation

“…Therefore, converting n-type MoS 2 to p-type by electron capture under the current low-energy (100 eV) He + ion irradiation is supposed to be accompanied by the migration of the topmost S atoms or its minimal sputtering. We note that it is possible to lower the kinetic energies of He + ions down to ~ 15 eV by using a commercial sputter ion gun equipped with a Wien-filter for mass/charge separation 57 . Further research needs to study the possibility of converting n-type supported MoS 2 monolayer into p-type without deteriorating its intrinsic functionality by using much lower energy of He + ion irradiation or using a capping layer like the overlayer graphene under the current He + ion irradiation 29 .…”

Imaging Momentum–Space Two‐Particle Correlations at Surfaces

“…[37,38] A modified sputter ion gun allowed the excitation of the surface with low-energy He þ and He 2þ ions. [39][40][41] Studies on Auger decay were conducted at the synchrotron light source BESSY II of the Helmholtz-Zentrum Berlin (HZB). We comment briefly on a new DPE setup which uses a light source based on high harmonics generation in combination with a pair of time-of-flight spectrometers.…”