Positron attachment to the He doubly excited states

TL;DR

This paper demonstrates the theoretical existence of positron attachment to specific doubly excited helium states, predicting their binding energies, resonance widths, and potential detectability in collision spectra using advanced computational methods.

Contribution

It introduces a new theoretical demonstration of positron attachment to doubly excited helium states with detailed energy and resonance width calculations.

Findings

Positron attachment states have specific binding energies.

Resonance widths were computed for key states.

A series of related resonances in helium were predicted.

Abstract

The projection method is used to demonstrate the existence of positron attachment to three doubly excited states of helium. The e^+He(2s^2 1Se), e^+He(3s^2 1Se), and the e^+He(2s2p 3Po) states have binding energies of 0.447eV, 0.256eV and 0.486eV respectively. These energies were computed with the stochastic variational method and the configuration interaction method. These states will exist as resonances in the e^+ + He continuum and the e^+He(2s^2 1Se) state could be detectable in the e^+ + He collision spectrum. A resonance width of 0.068eV was computed for the e^+He(2s^2 1Se), state by using the complex rotation method. The existence of a series of e^+He(ns^2 1Se) resonances associated with the He(ns^2) double Rydberg series is also predicted and an explicit calculation demonstrating the existence of the e^+He(3s^2 1Se) state is reported.