Journal of Physics Communications (Jan 2024)
Virtual and bound states in low-energy positron scattering by atoms and molecules via modified effective range theory
Abstract
Modified effective range theory is applied as a tool to determine bound and virtual state energies in low-energy positron elastic scattering by atoms and molecules. This is achieved by the S-matrix continuation into the complex momentum plane, allowing to identify poles related to shallow energy states. The influence of the long-range polarization potential (∼ r ^−4 ) on the bound and virtual-state pole positions is analyzed for noble gases and nonpolar molecules such as H _2 , N _2 , and CH _4 . The quantitative relations between the S-matrix poles and the s -wave scattering length accounting for dipole polarization are introduced.
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