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Spin-orbit-resolved resonant Auger spectrum of a dissociating HCl molecule

M. Žitnik, J. Turnšek, K. Bučar, and A. Mihelič

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Phys. Rev. A 114, 043111 – Published 16 October, 2026

DOI: https://doi.org/10.1103/ws2q-ky4n

Abstract

The photodissociation of HCl via the antibonding 2p−1σ* resonance occurs on the same 10-fs timescale as the Auger decay of the 2p vacancy. This means that the v,v′, and σ* valence molecular orbitals involved in the electronic transition can significantly differ from the orbitals at the ground state equilibrium internuclear position. The nonrelativistic L−vv′ resonant Auger (RA) spectrum based on the stationary Green's function approach gives a good estimate of relative intensities of the three main spectral features in the 173–182eV emission energy range, but fails to reproduce highly resolved experimental data. We show that addition of the spin-orbit interaction of the 2π−2σ* and 5σ−12π−1σ* final states significantly improves the agreement for the spectral feature arising from the 4Π,2Σ, and 4Σ states that converge to the H + Cl+(3P) dissociation limit. Somewhat surprisingly, we found that the P3 nonrelativistic limit splits to five instead of three 3p−2(3P0,1,2) dissociation limits of the Cl+ fragment at large internuclear distances. The similarity with the atomic case is broken because of a different nature of the 2Π molecular state, which is populated by a weak participator Auger decay and converges to a different, significantly higher H+ + Cl(P2) dissociation limit. Our analysis shows that the remaining differences with an angle-integrated experimental spectrum are caused primarily by inaccuracies of the nonrelativistic final state potentials and not by the one-center approximation of the spectator Auger transition rates. The potential slope differences are imprinted on the RA spectrum with a sensitivity and range depending on the duration of molecular dissociation with respect to the core-hole lifetime.

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Phys. Rev. A 114, 043111– Published 16 October, 2026
  • Received 13 August 2026
  • Accepted 1 October 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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