Vibronic dynamics in electron continuum -- iterative solvers

TL;DR

This paper develops and compares iterative Krylov-subspace methods for simulating vibronic resonance dynamics in electron-molecule collisions, including models with multiple vibrational degrees of freedom.

Contribution

It introduces a general 2D model of conical intersections involving metastable states and tests iterative solvers on this and larger models, advancing computational methods for resonance dynamics.

Findings

Krylov-subspace methods effectively simulate vibronic resonance dynamics.

Preconditioning schemes improve solver performance.

Methods are applicable to complex models with multiple vibrational degrees of freedom.

Abstract

We present a general two-dimensional model of conical intersection between metastable states that are vibronically coupled not only directly but also indirectly through a virtual electron in the autodetachment continuum. This model is used as a test ground for design and comparison of iterative solvers for resonance dynamics in low-energy electron-molecule collisions. Two Krylov-subspace methods with various preconditioning schemes are compared. To demonstrate the applicability of the proposed methods on even larger models, we also test the performance of one of the methods on a recent model of vibrational excitation of CO$_2$ by electron impact based on three vibronically-coupled discrete states in continuum (Renner-Teller doublet of shape resonances coupled to sigma virtual state) including four vibrational degrees of freedom. Two-dimensional electron energy-loss spectra resulting from the electron-molecule scattering within the models are briefly discussed.