Molecular Ion Desorption from LiF(110) Surfaces by Positron Annihilation

Area of Science:

• Surface science
• Materials science
• Atomic and molecular physics

Background:

• Understanding ion desorption from ionic crystal surfaces is crucial.
• Electron irradiation typically yields only atomic ions.

Purpose of the Study:

• To investigate the interaction between positrons and ionic crystals.
• To examine ion desorption from LiF(110) surfaces using positron and electron irradiation.

Main Methods:

• Irradiation of LiF(110) crystal surfaces with 500 eV positrons and electrons.
• Analysis of desorbed positive ions using mass spectrometry.
• Temperature-dependent measurements of ion yields.

Main Results:

• Electron irradiation desorbed only monatomic ions (H+, Li+, F+).
• Positron irradiation induced significant desorption of molecular ions (FH+, F2+).
• Molecular ion yields exhibited higher temperature sensitivity compared to atomic ions.

Conclusions:

• A novel desorption model is proposed involving the formation of surface positronic compounds.
• Positron annihilation triggers Auger decay, leading to the desorption of molecular ions.
• Positron irradiation offers a unique pathway for desorbing molecular species from ionic surfaces.