Bulletin of the American Physical Society
55th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Monday–Friday, June 3–7, 2024; Fort Worth, Texas
Session R04: Antimatter and Electron Collisions
2:00 PM–3:48 PM,
Thursday, June 6, 2024
Room: 201BC
Chair: Sandra Ward Quintanilla, University of North Texas
Abstract: R04.00001 : Atomic and molecular ion desorption from solid surfaces via positron annihilation*
2:00 PM–2:30 PM
Presenter:
Yasuyuki Nagashima
(Department of Physics, Tokyo University of Science)
Authors:
Yasuyuki Nagashima
(Department of Physics, Tokyo University of Science)
Takayuki Tachibana
(Department of Physics, Rikkyo University)
It has long been known that atoms on a solid surface are desorbed when the surface is irradiated by electrons with energies higher than the binding energy of the inner-shell electrons of the atoms constituting the surface. This phenomenon is explained as the inner-shell ionization caused by electron impact and the subsequent emission of Auger electrons, resulting in the atoms becoming positively divalent or more valence and desorbing due to Coulomb repulsion with the surrounding atoms [1]. The same phenomenon occurs in the case of low-energy positron bombardment [2]. However, there is no energy threshold in the case of positron bombardment, and the number of desorbed ions per incident particle is much higher than in the case of electron bombardment [3]. This phenomenon can be explained by the fact that the incident positrons are trapped on the surface as they diffuse back through the solid, and the atoms are desorbed by pair annihilation with the inner-shell electrons of the surface atoms.
Recently, it was discovered that F2+ ions desorb when a slow positron beam is injected onto a LiF surface [4]. This is in contrast to the case of electron irradiation, where only monatomic ions such as H+, Li+, and F+ are desorbed. This desorption of molecular ions by slow positrons is interpreted as the formation of e+[F-F-] at the surface, followed by the emission of Auger electrons by pair annihilation with the inner-shell electrons of the positrons, resulting in desorption as F2+. This technique may pave the way for the formation of new molecular ions that cannot be achieved by other methods.
*This work was supported by Grantsin-Aid for Scientific Research (KAKENHI; Grant No. JP20K12498).
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