# Multi-reference quantum chemistry protocol for simulating autoionization spectra: Test of ionization continuum models for the neon atom

## TL;DR

This paper introduces a quantum chemistry protocol combining electronic structure and continuum models to accurately simulate Auger decay spectra, validated on neon atom data.

## Contribution

The work presents a novel combined approach for calculating Auger decay rates using restricted active space methods and continuum orbitals, with systematic testing against reference data.

## Key findings

- Continuum orbital accuracy critically affects decay rate predictions.
- Auger energies are well reproduced with small active spaces.
- Direct Coulomb potential inclusion improves continuum wave functions.

## Abstract

In this contribution we present a protocol to evaluate partial and total Auger decay rates combining the restricted active space self-consistent field electronic structure method for the bound part of the spectrum and numerically obtained continuum orbitals in the single-channel scattering theory framework. On top of that, the two-step picture is employed to evaluate the partial rates. The performance of the method is exemplified for the prototypical Auger decay of the neon $1s^{-1}3p$ resonance. Different approximations to obtain the continuum orbitals, the partial rate matrix elements, and the electronic structure of the bound part are tested against theoretical and experimental reference data. It is demonstrated that the partial and total rates are most sensitive to the accuracy of the continuum orbitals. For instance, it is necessary to account for the direct Coulomb potential of the ion for the determination of the continuum wave functions. The Auger energies can be reproduced quite well already with a rather small active space. Finally, perspectives of the application of the proposed protocol to molecular systems are discussed.