Total photoionization cross-sections of excited electronic states by the algebraic diagrammatic construction-Stieltjes-Lanczos method.

Here, we extend the L2 ab initio method for molecular photoionization cross-sections introduced in Gokhberg et al. [J. Chem. Phys. 130, 064104 (2009)] and benchmarked in Ruberti et al. [J. Chem. Phys. 139, 144107 (2013)] to the calculation of total photoionization cross-sections of molecules in electronically excited states. The method is based on the ab initio description of molecular electronic states within the many-electron Green's function approach, known as algebraic diagrammatic construction (ADC), and on the application of Stieltjes-Chebyshev moment theory to Lanczos pseudospectra of the ADC electronic Hamiltonian. The intermediate state representation of the dipole operator in the ADC basis is used to compute the transition moments between the excited states of the molecule. We compare the results obtained using different levels of the many-body theory, i.e., ADC(1), ADC(2), and ADC(2)x for the first two excited states of CO, N2, and H2O both at the ground state and the excited state equilibrium or saddle point geometries. We find that the single excitation ADC(1) method is not adequate even at the qualitative level and that the inclusion of double electronic excitations for description of excited state photoionization is essential. Moreover, we show that the use of the extended ADC(2)x method leads to a substantial systematic difference from the strictly second-order ADC(2). Our calculations demonstrate that a theoretical modelling of photoionization of excited states requires an intrinsically double excitation theory with respect to the ground state and cannot be achieved by the standard single excitation methods with the ground state as a reference.

Total molecular photoionization cross-sections by algebraic diagrammatic construction-Stieltjes-Lanczos method: benchmark calculations.

In [K. Gokhberg, V. Vysotskiy, L. S. Cederbaum, L. Storchi, F. Tarantelli, and V. Averbukh, J. Chem. Phys. 130, 064104 (2009)] we introduced a new L(2) ab initio method for the calculation of total molecular photoionization cross-sections. The method is based on the ab initio description of discretized photoionized molecular states within the many-electron Green's function approach, known as algebraic diagrammatic construction (ADC), and on the application of Stieltjes-Chebyshev moment theory to Lanczos pseudospectra of the ADC electronic Hamiltonian. Here we establish the accuracy of the new technique by comparing the ADC-Lanczos-Stieltjes cross-sections in the valence ionization region to the experimental ones for a series of eight molecules of first row elements: HF, NH3, H2O, CO2, H2CO, CH4, C2H2, and C2H4. We find that the use of the second-order ADC technique [ADC(2)] that includes double electronic excitations leads to a substantial systematic improvement over the first-order method [ADC(1)] and to a good agreement with experiment for photon energies below 80 eV. The use of extended second-order ADC theory [ADC(2)x] leads to a smaller further improvement. Above 80 eV photon energy all three methods lead to significant deviations from the experimental values which we attribute to the use of Gaussian single-electron bases. Our calculations show that the ADC(2)-Lanczos-Stieltjes technique is a reliable and efficient ab initio tool for theoretical prediction of total molecular photo-ionization cross-sections in the valence region.

[B symptoms in unexplained mediastinal lymphadenopathy : Case report of a 72-year-old male patient with VEXAS syndrome]. / B-Symptomatik bei unklarer mediastinaler Lymphadenopathie : Fallbericht eines 72-jährigen Patienten mit VEXAS-Syndrom.

The case of a 72-year-old male patient who presented to our centre for rare diseases with recurrent fever, night sweats and weight loss with initially confirmed mediastinal lymphadenopathy is reported. Investigation of lymph node material was unrevealing. As an additional finding, the patient had a myelodysplastic syndrome. VEXAS syndrome (vacuoles, E1 enzyme, X­linked, autoinflammatory, somatic) could be confirmed on the basis of a bone marrow biopsy and genetic testing.

Quenching molecular photodissociation by intermolecular Coulombic decay.

In this paper we study the impact of interatomic Coulombic decay (ICD) on molecular photodissociation. The investigation reveals the hitherto unrecognized ability of ICD to quench processes involving nuclear rearrangements. Numerical computations of the nuclear dynamics, initiated by photoexciting the B(1)Σ(+) Rydberg state of CO in CO·Mg complexes, are carried out. The efficiencies of ICD and photoinduced predissociation are compared for the four lowest vibrational levels of the corresponding electronic state. We also show the impact of CO vibrations on the ICD electron spectrum. Finally, we discuss the growing efficiency of ICD to quench the dissociation as the number of neighboring Mg atoms is increased.

Ab initio interatomic decay widths of excited states by applying Stieltjes imaging to Lanczos pseudospectra.

Electronically excited states of atoms and molecules in an environment may decay in interatomic processes by transferring excess energy to neighboring species and ionizing them. The corresponding interatomic decay width is the most important characteristic of the decay allowing to calculate its efficiency and the final states' distribution. In this paper we present calculations of interatomic widths by the Fano-Stieltjes method applied to Lanczos pseudospectra, which has been previously shown to provide accurate autoionization widths in atoms and molecules. The use of Lanczos pseudospectra allows one to avoid the full diagonalization bottleneck and makes the method applicable to larger systems. We apply the present method to the calculation of interatomic decay widths in NeMg, NeAr and HCN[middle dot]Mg(n), n = 1, 2 clusters. The results are compared with widths obtained analytically and by other ab initio methods where available.

Autoionization widths by Stieltjes imaging applied to Lanczos pseudospectra.

Excited states of atoms and molecules lying above the ionization threshold can decay by electron emission in a process commonly known as autoionization. The autoionization widths can be calculated conveniently using Fano formalism and discretized atomic and molecular spectra by a standard procedure referred to as Stieltjes imaging. The Stieltjes imaging procedure requires the use of the full discretized spectrum of the final states of the autoionization, making its use for poly-atomic systems described by high-quality basis sets impractical. Following our previous work on photoionization cross-sections, here we show that also in the case of autoionization widths, the full diagonalization bottleneck can be overcome by the use of Lanczos pseudospectra. We test the proposed method by calculating the well-documented autoionization widths of inner-valence-excited neon and apply the new technique to autoionizing states of hydrofluoric acid and benzene.

Calculation of resonant interatomic Coulombic decay widths of inner-valence-excited states delocalized due to inversion symmetry.

Inner-valence-excited states of clusters can decay by electron emission via several of mechanisms, the leading ones being intra-atomic autoionization and resonant interatomic Coulombic decay. Recently, we have derived the Wigner-Weisskopf theory for the calculation of the decay widths of the inner-valence excitations [J. Chem. Phys. 124, 144315 (2006)]. While the new method has been successful in producing the decay rates of heteronuclear diatomic clusters, it cannot be applied to systems possessing inversion symmetry, e.g., to homonuclear diatoms, due to delocalization of the molecular orbitals involved in the decay processes. In the present work, we show that the Wigner-Weisskopf theory of the decay of inner-valence-excited states can be generalized to systems with inversion symmetry using a technique of adapted final states [J. Chem. Phys. 125, 094107 (2006)]. The same technique can be employed when going beyond the Wigner-Weisskopf theory. We consider the experimentally relevant case of competing resonant interatomic Coulombic decay and autoionization in neon dimer and calculate the rates of these processes for a series of inner-valence-excited states which has been measured by Aoto et al. [Phys. Rev. Lett. 97, 243401 (2006)].