Resonant Auger spectroscopy at the carbon and nitrogen K-edges of pyrimidine

The Journal of Chemical Physics

2020

We present the application of the spherically averaged continuum model to the evaluation of molecular photoelectron and resonant Auger electron spectra. In this model, the continuum wave function is obtained in a numerically efficient way by solving the radial Schrödinger equation with a spherically averaged molecular potential. Different approximations to the Auger transition matrix element and, in particular, the onecenter approximation are thoroughly tested against experimental data for the CH 4 , O 2 , NO 2 , and pyrimidine molecules. In general, this approach appears to estimate the shape of the photoelectron and autoionization spectra as well as the total Auger decay rates with reasonable accuracy, allowing for the interpretation of experimental results.

Section: Pyrimidinesupporting

confidence: 91%

“…b. PES and RAES The predicted PES at 397 eV and the RAES obtained at the E6 resonance together with experimental data digitized from Bolognesi et al 77 are compiled in Fig. 4 (b).…”

Section: Pyrimidinementioning

confidence: 99%

Multi-reference protocol for (auto)ionization spectra: Application to molecules

Grell

The Journal of Chemical Physics

2020

“…The 1s N → π * (2a 2 ) core-excited energy of pyrimidine was calculated at 398.13 eV and 398.81 eV with QC-I and QC-II, respectively, whereas the measured reference value is 398.8 eV. 82 Thus, both QC schemes reproduce the inner-shell excited state energy quite accurately. As for the resonant Auger, we start with the analysis of Fig.…”

Section: Pyrimidine C 4 H 4 Nmentioning

confidence: 94%

“…We tested our OCA-RASPT2 approach by computing the Auger spectra (either AES, RAES or both) of Ne, CO, N 2 , HNCO, H 2 O, NO 2 and C 4 N 2 H 4 (pyrimidine) and comparing our results with available experimental data. [77][78][79][80][81][82] We used experimental geometries obtained from the NIST WebBook, 83 except for pyrimidine where the geometry was optimized at the B3LYP/def2-TZVP 84 level using Turbomole. 85 Dunning correlation-consistent basis sets were used throughout.…”

Section: Computational Detailsmentioning

confidence: 99%

“…Since three nucleobases, thymine, cytosine and uracil, are pyrimidine derivatives, pyrimidine has been used as a common prototype system in numerous studies aimed at understanding the basics mechanisms involved in photoinduced DNA damage. 82,[108][109][110][111][112][113][114] We base our computational analysis on the recent XAS and RAES measurements at the nitrogen K-edge of Bolognesi et al 82 A theoretical study has been recently reported for the XAS, RAES and PES of pyrimidine by Grell and Bokarev. 65 65 In that report, the authors obtained resonant Auger spectra at the nitrogen K-edge based on the RASPT2 approximation level and the SCI.…”

Section: Pyrimidine C 4 H 4 Nmentioning

confidence: 99%

See 1 more Smart Citation

Multi-Reference Approach to Normal and Resonant Auger Spectra Based on the One-Center Approximation

Tenório

Voß

et al. 2022

Preprint

A methodology to calculate the decay rates of normal and resonant Auger processes in atoms and molecules based on the One-Center Approximation (OCA) using atomic radial Auger integrals is implemented within the restricted-active-space self-consistent-field (RASSCF) and multi-state restricted-active-space perturbation theory of second order (MS-RASPT2) frameworks as part of the OpenMolcas project. To ensure an unbiased description of the correlation and relaxation effects on the initial core excited/ ionized states and the final cationic states, their wave functions are optimized independently, whereas the Auger matrix elements are computed with a biorthonormalized set of molecular orbitals within the state-interaction (SI) approach. As a decay of an isolated resonance, the computation of Auger intensities involves matrix elements with one electron in the continuum. However, treating ionization and autoionization problems can be overwhelmingly complicated for non-experts because of many peculiarities in comparison to bound-state electronic structure theory. One of the advantages of our approach is that, by projecting the intensities on the atomic center bearing the core hole and using precalculated atomic radial two-electron integrals, the Auger decay rates can be easily obtained directly with OpenMolcas, avoiding the need to interface it with external programs to compute matrix elements with the photoelectron wave function. The implementation is tested on the Ne atom, for which numerous theoretical and experimental data are available for comparison, as well as on a set of prototype closed- and open-shell molecules, namely, CO, N2, HNCO, H2O, NO2, and C4N2H4 (pyrimidine).

Multireference Approach to Normal and Resonant Auger Spectra Based on the One-Center Approximation

Tenório

Voß

J. Chem. Theory Comput.

et al. 2022

A methodology to calculate the decay rates of normal and resonant Auger processes in atoms and molecules based on the One-Center Approximation (OCA), using atomic radial Auger integrals, is implemented within the restricted-active-space self-consistent-field (RASSCF) and the multistate restricted-active-space perturbation theory of second order (MS-RASPT2) frameworks, as part of the OpenMolcas project. To ensure an unbiased description of the correlation and relaxation effects on the initial core excited/ionized states and the final cationic states, their wave functions are optimized independently, whereas the Auger matrix elements are computed with a biorthonormalized set of molecular orbitals within the state-interaction (SI) approach. As a decay of an isolated resonance, the computation of Auger intensities involves matrix elements with one electron in the continuum. However, treating ionization and autoionization problems can be overwhelmingly complicated for nonexperts, because of many peculiarities, in comparison to bound-state electronic structure theory. One of the advantages of our approach is that by projecting the intensities on the atomic center bearing the core hole and using precalculated atomic radial two-electron integrals, the Auger decay rates can be easily obtained directly with OpenMolcas , avoiding the need to interface it with external programs to compute matrix elements with the photoelectron wave function. The implementation is tested on the Ne atom, for which numerous theoretical and experimental results are available for comparison, as well as on a set of prototype closed- and open-shell molecules, namely, CO, N 2 , HNCO, H 2 O, NO 2 , and C 4 N 2 H 4 (pyrimidine).