Broad advances in the capabilities of controlling and spectroscopic investigation of molecules have enabled new scientific discoveries in molecular structure and interaction dynamics. We will present examples for some of the latest work.

This talk addresses quantum dynamical studies of ultrafast photo-induced energy and charge transfer in functional organic materials, complementing time-resolved spectroscopic observations [1] which underscore that the elementary transfer events in these molecular aggregate systems can be guided by quantum coherence, despite the presence of static and dynamic disorder. The intricate interplay of electronic delocalization, coherent vibronic dynamics, and trapping phenomena requires a quantum dynamical treatment that goes beyond conventional mixed quantum-classical simulations. Our approach combines first-principles parametrized Hamiltonians, based on TDDFT and/or high-level electronic structure calculations, with accurate quantum dynamics simulations using the Multi-Configuration Time-Dependent Hartree (MCTDH) method [2]. The talk will specifically focus on (i) exciton dissociation and free carrier generation in regioregular donor-acceptor assemblies [3-5], (ii) exciton multiplication in acene materials [6] and (iii) the elementary mechanism of exciton migration and creation of charge-transfer excitons in polythiophene and poly-(p-phenylene vinylene) type materials [7]. Special emphasis is placed on the influence of structural (dis)order and molecular packing, which can act as a determining factor in transfer efficiencies. Against this background, we will comment on the role of temporal and spatial coherence along with a consistent description of the transition to a classical-statistical regime. [1] A. De Sio and C. Lienau, Phys. Chem. Chem. Phys. 19, 18813 (2017). [2] G. A. Worth, H.-D. Meyer, H. Köppel, L. S. Cederbaum, and I. Burghardt, Int. Rev. Phys. Chem. 27, 569 (2008). [3] M. Polkehn, H. Tamura, P. Eisenbrandt, S. Haacke, S. Méry, and I. Burghardt, J. Phys. Chem. Lett. 7, 1327 (2016). [4] M. Polkehn, P. Eisenbrandt, H. Tamura, and I. Burghardt, Int. J. Quantum Chem. 118:e25502. (2018). [5] M. Polkehn, H. Tamura, and I. Burghardt, J. Phys. B: At. Mol. Opt. Phys. 51, 014003 (2018). [6] H. Tamura, M. Huix-Rotllant, I. Burghardt, Y. Olivier, and D. Beljonne, Phys. Rev. Lett. 115, 107401 (2015). [7] R. Binder, M. Polkehn, T. Ma, and I. Burghardt, Chem. Phys. 482, 16 (2017).

Metal oxide clusters possess electronic, chemical, and physical properties that reflect the complex properties of defective bulk metal oxide materials, the importance of which is difficult to overstate when considering their ubiquity in applications ranging from catalysis to spintronics. Choice of binary metal combinations adds an important dimension in efforts to enhance and tune the properties of oxides, which are further affected by manipulating the oxidation state. We have explored the intrinsically local phenomena arising from mixed metal oxides, particularly in lower-than-traditional oxidation states (sub-oxides), by applying anion photoelectron spectroscopy and density functional theory calculations to the study of small mixed metal sub-oxide clusters. Anion photoelectron spectroscopy is a mass-selective method that probes the energies of the manifold of low-lying electronic states inherent in neutral sub-oxide species. By coupling experimental with computational results, a detailed picture of how mixed metal composition impacts molecular and electronic structure emerges. For example, profoundly asymmetric metal-oxygen bond formation in near-neighbor mixed transition or lanthanide metal oxides can be reconciled with relative oxophilicities, and the prevalence of antiferromagnetic spin states can be reconciled with localization of metal atomic orbitals in mixed systems. Striking charge separation is observed in trans-periodic mixed metal oxides that combine transition and post-transition metals, or transition and lanthanide metals, combinations that are evocative of strongly-interacting catalyst-support systems. Finally, we consider whether more can be gleaned from anion photoelectron spectroscopy of these exceptionally complex systems by exploiting the electron-kinetic-energy-dependent neutral-electron interactions.

Criegee intermediates, carbonyl oxides produced in ozonolysis of unsaturated hydrocarbons, play important roles in atmospheric chemistry. A new production scheme using photolysis of R₂CI₂ + O₂ facilitated the production and direct detection of Criegee intermediates with various spectral techniques and has stimulated rapidly expanding research.Y.-P.  Lee, J. Chem. Phys. 143, 020901 (2015).^,D. L.  Osborn, C. A.  Taatjes, Int. Rev. Phys. Chem. 34, 309 (2015).ur understanding of important atmospheric reactions involving Criegee intermediates is becoming clarified because of the direct probing of Criegee intermediates in kinetic experiments. The infrared spectra of CH_2OO, Y. T.  Su, Y.−H.  Huang, H. A.  Witek, Y.−P.  Lee, Science 340, 174 (2013).^,Y.-H.  Huang, J.  Li, H.  Guo, Y.-P.  Lee, J. Chem. Phys. 142, 214301 (2015).H₃CHOO,H.-Y.  Lin, Y.-H.  Huang, X.  Wang, J. M.  Bowman, Y.  Nishimura, H. A.  Witek, Y.-P.  Lee, Nature Comm. 6, 7012 (2015).nd (CH3)₂COOY.-Y.  Wang, C.-Y.  Chung, Y.-P.  Lee, J. Chem. Phys. 145, 154303 (2016).ave been recorded with a step-scan FTIR with resolution 0.25 to 1 cm⁻¹; rotational contours with unresolved rotational lines were reported. On employing a quantum cascade laser coupled with a Herriot cell, we recorded spectra of the O-O stretching bands of CH₂OO and CH₃CHOO in the region 880-932 cm⁻¹ at resolution 0.002 cm⁻¹. In addition to improved rotational parameters, perturbation was observed at high-J levels of K_a = 3, 6, and 11 of CH₂OO. Distinct lines of syn- and anti-CH₃CHOO were also observed. Kinetic investigations based on this new experimental scheme will be presented. Taking advantage of the wide spectral coverage of an FTIR, we investigated the mechanism of the reactions of CH₂OO with SO₂, HNO₃, HCl, and HCOOH. For example, in the reaction of CH₂OO + HCOOH, eight observed bands are assigned to hydroperoxymethyl formate HPMF (P5). In the later reaction period, three bands are assigned to an isomer HPMF (P6) and three bands to the final product, anti-FAN. According to our kinetic analysis, only P5, not P6, decomposes to form FAN.

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Footnotes:

Y.-P.  Lee, J. Chem. Phys. 143, 020901 (2015).\end D. L.  Osborn, C. A.  Taatjes, Int. Rev. Phys. Chem. 34, 309 (2015).O\end Y. T.  Su, Y.−H.  Huang, H. A.  Witek, Y.−P.  Lee, Science 340, 174 (2013). Y.-H.  Huang, J.  Li, H.  Guo, Y.-P.  Lee, J. Chem. Phys. 142, 214301 (2015).C H.-Y.  Lin, Y.-H.  Huang, X.  Wang, J. M.  Bowman, Y.  Nishimura, H. A.  Witek, Y.-P.  Lee, Nature Comm. 6, 7012 (2015).a Y.-Y.  Wang, C.-Y.  Chung, Y.-P.  Lee, J. Chem. Phys. 145, 154303 (2016).h