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Université de Fribourg

Resonance raman optical activity shows unusual structural sensitivity for systems in resonance with multiple excited states: vitamin B12 case

Machalska, Ewa ; Zajac, Grzegorz ; Gruca, Anna ; Zobi, Fabio ; Baranska, Malgorzata ; Kaczor, Agnieszka

In: The Journal of Physical Chemistry Letters, 2020, vol. 11, no. 13, p. 5037–5043

In this work, cobalamins with different upper axial substituents and a cobalamin derivative with a ring modification were studied using chiroptical spectroscopies, in particular resonance Raman optical activity (RROA), to shed light on the influence of structural modifications on RROA spectra in these strongly chiral systems in resonance with multiple excited states at 532 nm excitation. We...

Université de Fribourg

Signatures of bosonic excitations in high-harmonic spectra of Mott insulators

Lysne, Markus ; Murakami, Yuta ; Werner, Philipp

In: Physical Review B, 2020, vol. 101, no. 19, p. 195139

The high-harmonic spectrum of the Mott insulating Hubbard model has recently been shown to exhibit plateau structures with cutoff energies determined by nth-nearest- neighbor doublon-holon recombination processes. The spectrum thus allows one to extract the on-site repulsion U. Here, we consider generalizations of the single-band Hubbard model and discuss the signatures of bosonic excitations...

Université de Fribourg

Adsorption-induced kondo effect in metal-free phthalocyanine on Ag(111)

Granet, J. ; Sicot, M. ; Gerber, I. C. ; Kremer, Geoffroy ; Pierron, T. ; Kierren, B. ; Moreau, L. ; Fagot-Revurat, Y. ; Lamare, S. ; Chérioux, F. ; Malterre, D.

In: The Journal of Physical Chemistry C, 2020, vol. 124, no. 19, p. 10441–10452

We report on the formation of a two-dimensional supramolecular Kondo lattice made of organic molecules comprising only C, N, and H atoms, namely metal-free phthalocyanines 2HPc (C32H18N8), adsorbed on a Ag(111) surface. Low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/STS), ultraviolet photoemission spectroscopy (UPS), and density functional theory (DFT) are used to...

Université de Fribourg

Thermal energy transport across the interface between phase change material n-heneicosane in solid and liquid phases and few-layer graphene

Chilukoti, Hari Krishna ; Zhou, Tianhang ; Ardham, Vikram Reddy ; Böhm, Michael C. ; Müller-Plathe, Florian

In: The Journal of Physical Chemistry C, 2019, vol. 123, no. 48, p. 29192–29202

Molecular dynamics simulations have been performed to investigate the mechanism of thermal energy transport at the interface between n-heneicosane in solid and liquid phases and few-layer graphene at different temperatures under two heating modes (in the “heat-matrix” mode, heat is flowing from the heated heneicosane molecules to the cooled ones through the graphene layers and in the...

Université de Fribourg

Coupling of electronic and nuclear motion in a negative ion resonance: Experimental and theoretical study of benzene

Allan, Michael ; Čurík, Roman ; Čársky, Petr

In: The Journal of Chemical Physics, 2019, vol. 151, no. 6, p. 064119

We present calculated and measured elastic and vibrational excitation cross sections in benzene with the objective to assess the reliability of the theoretical method and to shed more light on how the electronic motion of the incoming electron is coupled with the nuclear motion of the vibrations. The calculation employed the discrete momentum representation method which involves solving the...

Université de Fribourg

Laboratory based XAS measurements, electron-induced double K-shell ionization of Sc, Cr and Cu : and, Chemical sensitivity of photoinduced Kʰβ hypersatelite transition in Cr compounds

Zeeshan, Faisal ; Dousse, Jean-Claude (Dir.)

Thèse de doctorat : Université de Fribourg, 2017 ; no. 2052.

Cette thèse de doctorat contient trois différents projets qui appartiennent aux domaines de la physique atomique des couches profondes et de la spectroscopie de rayons X en haute résolution. Le premier projet concerne l’étude des spectres d’absorption (XAS) K et L de quelques éléments de transition 3d, 4d et 5d. Les mesures ont été réalisées à Fribourg avec le spectromètre à...

Université de Fribourg

High-harmonic generation in quantum spin systems

Takayoshi, Shintaro ; Murakami, Yuta ; Werner, Philipp

In: Physical Review B, 2019, vol. 99, no. 18, p. 184303

We theoretically study the high-harmonic generation (HHG) in one-dimensional spin systems. While in electronic systems the driving by ac electric fields produces radiation from the dynamics of excited charges, we consider here the situation where spin systems excited by a magnetic field pulse generate radiation via a time- dependent magnetization. Specifically, we study the magnetic dipole...