Physical Review Research (Nov 2023)

ASTRA: Transition-density-matrix approach to molecular ionization

  • Juan M. Randazzo,
  • Carlos Marante,
  • Siddhartha Chattopadhyay,
  • Barry I. Schneider,
  • Jeppe Olsen,
  • Luca Argenti

DOI
https://doi.org/10.1103/PhysRevResearch.5.043115
Journal volume & issue
Vol. 5, no. 4
p. 043115

Abstract

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We describe astra (attosecond transitions), a close-coupling approach to molecular ionization that uses many-body transition-density matrices between ionic states with arbitrary spin and symmetry, in combination with hybrid integrals between Gaussian and numerical orbitals, to efficiently evaluate photoionization observables. Within the transition-density-matrix approach, the evaluation of interchannel coupling is exact and does not depend on the size of the configuration-interaction space of the ions. Thanks to these two crucial features, astra opens the way to studying highly correlated and comparatively large targets at a manageable computational cost. Here, astra is used to predict the parameters of bound and autoionizing states of the boron atom and of the N_{2} molecule, as well as the total photoionization cross section of boron, the nitrogen molecule (N_{2}), and formaldehyde (H_{2}CO). Our results are in excellent agreement with theoretical and experimental values from the literature.