Channel-specific core-valence projectors for determining partial Auger decay widths

Matz, Florian; Jagau, Thomas-C.

doi:10.1080/00268976.2022.2105270

Cited by 8 publications

(31 citation statements)

References 64 publications

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“…We previously demonstrated that total and partial Auger decay widths can be extracted from CBF-EOMIP-CCSD wave functions of core-ionized states. [67][68][69] The decay is represented in these wave functions by 2h1p-excitations that fill the core hole. The resulting configurations give rise to the metastable character and are responsible for convergence problems when methods are used that do not treat the decay properly.…”

Section: Determination Of Auger Decay Widths With Complex-variable Me...mentioning

confidence: 99%

“…To obtain the partial width for a channel, one needs to solve the EOMIP-CCSD equations for the core-ionized state under the constraint that the amplitudes for this particular channel are zero, which we previously referred to as Auger Channel Projector (ACP). 68 The difference in the total width with and without the channel being present is then interpreted as partial width.…”

Section: Determination Of Auger Decay Widths With Complex-variable Me...mentioning

confidence: 99%

“…The CBF approach is related to complex scaling 65,66 and has been shown to yield accurate total and partial Auger decay widths. [67][68][69] CBF methods are capable of describing the bound and unbound parts of a resonance state at once; there is no need to impose an explicit form for the wave function of the Auger electron.…”

Section: Introductionmentioning

confidence: 99%

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Ab initio investigation of the Auger spectra of methane, ethane, ethylene, and acetylene

Matz

Nijssen

Jagau

2023

Preprint

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We present an ab initio computational study of the Auger spectra of methane, ethane, ethylene, and acetylene. Auger spectroscopy is a established technique to probe the electronic structure of molecules and exploits the Auger-Meitner effect that coreionized states produced by X-ray irradiation undergo. We compute partial decay widths for the relevant decay channels using coupled-cluster theory with single and double substitutions (CCSD) and equation-of-motion-CCSD theory combined with complex-scaled basis functions and Feshbach-Fano projection. We generate Auger spectra from these partial widths and draw conclusions about the strength of particular decay channels and trends between the four molecules. A connection to experimental results about fragmentation pathways of the electronic states produced by Auger decay is also made.

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Section: Determination Of Auger Decay Widths With Complex-variable Me...mentioning

confidence: 99%

Section: Determination Of Auger Decay Widths With Complex-variable Me...mentioning

confidence: 99%

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Ab initio investigation of the Auger spectra of methane, ethane, ethylene, and acetylene

Matz

Nijssen

Jagau

2023

Preprint

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“…[111][112][113][114] To compute partial Auger decay widths in the framework of the CBF approach, Matz and Jagau developed two different procedures. 76,77 The first one can be viewed as a generalization of CVS 35 . In this procedure, partial widths are evaluated by applying projectors that are specific to a particular Auger decay channel.…”

Section: Complex Basis Function Approachmentioning

confidence: 99%

“…In this procedure, partial widths are evaluated by applying projectors that are specific to a particular Auger decay channel. 77 The approach works well combined with CCSD, EOM-CCSD, and configuration interaction singles (CIS) wave functions but has the disadvantage that each decay channel requires a separate calculation.…”

Section: Complex Basis Function Approachmentioning

confidence: 99%

The Auger spectrum of benzene

Jayadev

Ferino-Pérez

Matz

et al. 2023

Preprint

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We present an ab initio computational study of the Auger electron spectrum of benzene. Auger electron spectroscopy exploits the Auger-Meitner effect and, although it is established as an analytic technique, the theoretical modeling of molecular Auger spectra from first principles remain challenging. Here, we use coupled-cluster and equation-of-motion coupled-cluster theory combined with two approaches to describe the decaying nature of core-ionized states: (i) Feshbach-Fano resonance theory and (ii) the method of complex basis functions. The spectra computed with these two approaches are in excellent agreement with each other and also agree well with experimental Auger spectra of benzene. The Auger spectrum of benzene features two well-resolved peaks at Auger electron energies above 260 eV that correspond to final states with two electrons removed from the 1e1g and 3e2g highest occupied molecular orbitals. At lower Auger electron energies, the spectrum is less well resolved and the peaks comprise multiple final states of the benzene dication. In line with theoretical considerations, singlet decay channels contribute more to the total Auger intensity than the corresponding triplet decay channels.

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State-Specific Coupled-Cluster Methods for Excited States

Damour,

Scemama,

Jacquemin

et al. 2024

J. Chem. Theory Comput.

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We reexamine ΔCCSD, a state-specific coupledcluster (CC) with single and double excitations (CCSD) approach that targets excited states through the utilization of non-Aufbau determinants. This methodology is particularly efficient when dealing with doubly excited states, a domain in which the standard equation-of-motion CCSD (EOM-CCSD) formalism falls short. Our goal here to evaluate the effectiveness of ΔCCSD when applied to other types of excited states, comparing its consistency and accuracy with EOM-CCSD. To this end, we report a benchmark on excitation energies computed with the ΔCCSD and EOM-CCSD methods for a set of molecular excited-state energies that encompasses not only doubly excited states but also doublet− doublet transitions and (singlet and triplet) singly excited states of closed-shell systems. In the latter case, we rely on a minimalist version of multireference CC known as the two-determinant CCSD method to compute the excited states. Our data set, consisting of 276 excited states stemming from the QUEST database [Veŕil et al., WIREs Comput. Mol. Sci. 2021, provides a significant base to draw general conclusions concerning the accuracy of ΔCCSD. Except for the doubly excited states, we found that ΔCCSD underperforms EOM-CCSD. For doublet−doublet transitions, the difference between the mean absolute errors (MAEs) of the two methodologies (of 0.10 and 0.07 eV) is less pronounced than that obtained for singly excited states of closed-shell systems (MAEs of 0.15 and 0.08 eV). This discrepancy is largely attributed to a greater number of excited states in the latter set exhibiting multiconfigurational characters, which are more challenging for ΔCCSD. We also found typically small improvements by employing state-specific optimized orbitals.

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Channel-specific core-valence projectors for determining partial Auger decay widths

Cited by 8 publications

References 64 publications

Ab initio investigation of the Auger spectra of methane, ethane, ethylene, and acetylene

Ab initio investigation of the Auger spectra of methane, ethane, ethylene, and acetylene

The Auger spectrum of benzene

State-Specific Coupled-Cluster Methods for Excited States

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