WELCOME AND INTRODUCTIONS

This talk will provide an introduction to this mini-symposium, which features advances in high-harmonic generation and the spectroscopy it enables. This strong-field process is a sensitive probe of small-molecule electronic structure, as the spectrum of the extreme ultraviolet (XUV) photons produced by the ionization-recollision process measures the shape and energy of the molecular orbitals. Furthermore, the XUV pulse can be used as an element-specific probe of electron dynamics in molecules and materials at femtosecond to attosecond timescales

FEMTOSECOND EXTREME ULTRAVIOLET SPECTROSCOPY OF SEMICONDUCTOR CARRIER DYNAMICS

Extreme ultraviolet (XUV) transient absorption spectroscopy is emerging as a powerful, element-specific tool for measuring femtosecond to attosecond dynamics in molecular and solid-state systems. Tabletop XUV transient absorption spectra retain the element specificity of hard x-ray absorption while providing a straightforward mapping of the unoccupied valence and conduction band density of states. The presence of distinct signals for holes and electrons in the XUV region is especially powerful, as the dynamics of these carriers are often convolved in transient UV/visible measurements. In this work we measure the rate of charge transfer across TiO2/CH3NH3PbI3 and CH3NH3PbI3/NiO interfaces, and highlight the competition between carrier cooling in the perovskite absorber and charge injection into the electron/hole collection layer

FEMTOSECOND ELEMENT-SPECIFIC XUV SPECTROSCOPY OF COMPLEX MOLECULES AND MATERIALS

Systems with multiple heavy atoms, such as the multimetallic clusters favored by Nature for redox catalysis and emerging photovoltaic materials such as CH$_{3}$NH$_{3}$PbI$_{3}$, pose challenges for traditional spectroscopic techniques. The growing field of high-harmonic extreme ultraviolet spectroscopy combines the element-, oxidation state-, spin state-, and ligand field specificity of XANES spectroscopy with the femtosecond time resolution of tabletop Ti:Sapphire lasers. We will show that this technique can be used to measure the photophysics of transition metal complexes, organohalide perovskites, and even small metalloproteins, extending the technique to mainstream problems in physical and inorganic chemistry

Багатомовність в Україні та її специфіка

У статті висвітлюються аспекти явища багатомовності, характерні для України як для національної держави, котра продовжує перебувати на стадії трансформації державно-політичної, соціально-економічної, духовної систем. Підкреслюється актуальність «аксіоми національної державності», згідно з якою українська мова, яка є рідною для більшості членів титульної нації країни, має бути єдиною державною мовою.The article studies the aspects of the phenomenon of multilingualism which are characteristic of Ukraine as a national state that remains at the stage of final forming complicated by the transformation of state political, social, economic and spiritual systems. The author underlines actuality of “the axiom of national statehood” that expects Ukrainian to be official language because it is native for the most of members of a titular nation in Ukraine

Intraligand Charge Transfer Enables Visible‐Light‐Mediated Nickel‐Catalyzed Cross‐Coupling Reactions

We demonstrate that several visible‐light‐mediated carbon−heteroatom cross‐coupling reactions can be carried out using a photoactive NiII precatalyst that forms in situ from a nickel salt and a bipyridine ligand decorated with two carbazole groups (Ni(Czbpy)Cl2). The activation of this precatalyst towards cross‐coupling reactions follows a hitherto undisclosed mechanism that is different from previously reported light‐responsive nickel complexes that undergo metal‐to‐ligand charge transfer. Theoretical and spectroscopic investigations revealed that irradiation of Ni(Czbpy)Cl2 with visible light causes an initial intraligand charge transfer event that triggers productive catalysis. Ligand polymerization affords a porous, recyclable organic polymer for heterogeneous nickel catalysis of cross‐coupling reactions. The heterogeneous catalyst shows stable performance in a packed‐bed flow reactor during a week of continuous operation

WELCOME AND INTRODUCTIONS

This talk will provide an introduction to this mini-symposium, which features advances in high-harmonic generation and the spectroscopy it enables. This strong-field process is a sensitive probe of small-molecule electronic structure, as the spectrum of the extreme ultraviolet (XUV) photons produced by the ionization-recollision process measures the shape and energy of the molecular orbitals. Furthermore, the XUV pulse can be used as an element-specific probe of electron dynamics in molecules and materials at femtosecond to attosecond timescales

FEMTOSECOND EXTREME ULTRAVIOLET SPECTROSCOPY OF SEMICONDUCTOR CARRIER DYNAMICS

Extreme ultraviolet (XUV) transient absorption spectroscopy is emerging as a powerful, element-specific tool for measuring femtosecond to attosecond dynamics in molecular and solid-state systems. Tabletop XUV transient absorption spectra retain the element specificity of hard x-ray absorption while providing a straightforward mapping of the unoccupied valence and conduction band density of states. The presence of distinct signals for holes and electrons in the XUV region is especially powerful, as the dynamics of these carriers are often convolved in transient UV/visible measurements. In this work we measure the rate of charge transfer across TiO2/CH3NH3PbI3 and CH3NH3PbI3/NiO interfaces, and highlight the competition between carrier cooling in the perovskite absorber and charge injection into the electron/hole collection layer

Femtosecond extreme ultraviolet spectroscopy of an iridium photocatalyst reveals oxidation state and ligand field specific dynamics

Femtosecond X-ray absorption spectroscopy at the Ir O3-edge and N6,7-edges is performed on the photocatalyst iridium(III) tris(2-phenylpyridine), Ir(III)(ppy)3 using a tabletop high-harmonic source. Extreme ultraviolet (XUV) absorption between 44 eV and 72 eV measures transitions from the Ir 5p3/2 and 4f5/2,7/2 core to 5d valence orbitals, and the position of these spectral features is shown to be sensitive to the oxidation state and ligand field of the metal center. Upon excitation of the singlet metal-to-ligand charge transfer (1MLCT) band at 400 nm, a shift in the spectra due to the formation of the Ir(IV) center is observed, as is the creation of a new spectral feature corresponding to transitions into the t2g hole. Vibrational cooling of the MLCT state on the 3 ps and 16 ps timescales is measured as changes in the intensity of the transient features. This work establishes XUV spectroscopy as a useful tool for measuring the electronic structure of 3rd row transition metal photosensitizers and catalysts at ultrafast timescales