Fundamental studies of chemical reactions often draw molecular dynamics along a reaction coordinate in a calculated or suggested potential energy surface (PES) 1-5 . But fully mapping such dynamics experimentally, by following all nuclear motions in a timeresolved manner, that is the motions of wavepackets, is challenging and has not even been realized for the simple stereotypical bimolecular reaction 6-8 of A-B + C → A + B-C. Here we report such tracking of vibrational wavepacket trajectories during photo-induced bond formation in the gold trimer complex [Au(CN)2 -]3 in an aqueous solution, using femtosecond x-ray solution scattering (liquidography 9-12 ) at x-ray free electron lasers 13,14 . We find that the complex forms from an assembly of three monomers A, B and C clustered together through non-covalent interactions 15,16 and with the distance between A and B shorter than between B and C. Tracking of the wavepacket in three-dimensional nuclear coordinates (RAB, RBC, and RAC) reveals that within the first 60 fs after photoexcitation, a covalent bond forms between A and B to give A-B + C. The second covalent bond, between B and C, subsequently forms within 360 fs to give a linear and covalently-bonded trimer complex A-B-C. The trimer exhibits harmonic vibrations that we are also able to map, and unambiguously assign to specific normal modes using only the experimental data. More intense x-rays can in principle visualize the motion of not only highly-scattering atoms such as gold but also of lighter atoms such as carbon and nitrogen, which will open the door for the direct tracking of the atomic motions involved in many chemical reactions.The [Au(CN)2 -]3 complex has served as a valuable model system for studying photoinitiated processes in solution. Irradiation with ultraviolet light excites it from the ground state (S0) to the singlet state (S1), which within 20 fs undergoes intersystem crossing to reach a triplet excited state (T1') 18 . A further transition from T1' to another triplet excited state (T1) then occurs with a time constant of 1~2 ps, completing formation of covalent bonds and transformation of the complex from a bent to a linear structure 9,17,18 (see the Supplementary Information (SI) for details of the notations of electronic states).Formation of the bonds could involve any of the three possible candidate trajectories sketched in Fig. 1b. The equilibrium structure in the ground state determines the position of the

Bismuth triiodide, BiI3, is one of the simplest bismuth halides, which have recently attracted considerable attention because of their promising properties. Here, we investigate the structural dynamics of a photoinduced reaction of BiI3 in solution phase using time-resolved X-ray liquidography (TRXL) and density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. The photoreaction was initiated by excitation at 400 nm, which corresponds to the ligand-to-metal charge-transfer transition. The detailed structures and kinetic profiles of all relevant intermediate species from the TRXL data show that the trigonal planar structure of BiI3, which is predicted to be the most stable structure of the lowest excited state by TDDFT calculation, was not observed, and the photoreaction proceeds via two parallel pathways within the time resolution of 100 ps: (i) isomer formation to produce iso-BiI2–I, which relaxes back to the ground-state structure, and (ii) dissociation into BiI2· and I· radicals, which nongeminately recombine to generate ground-state BiI3 and I2.

Salt bridge, one of the representative structural factors established by non-covalent interactions, plays a crucial role in stabilizing the structure and regulating the protein function, but its role in dynamic...

The quaternary transition between the relaxed (R) and tense (T) states of heme-binding proteins is a textbook example for the allosteric structural transition. Homodimeric hemoglobin (HbI) from Scapharca inaequivalvis is a useful model system for investigating the allosteric behavior because of the relatively simple quaternary structure. To understand the cooperative transition of HbI, wild-type and mutants of HbI have been studied by using time-resolved X-ray solution scattering (TRXSS), which is sensitive to the conformational changes. Herein, we review the structural dynamics of HbI investigated by TRXSS and compare the results of TRXSS with those of other techniques.

We report the generation of gold nanoparticles (AuNPs) from the aqueous solution of chloro(2,2′,2″-terpyridine)gold(III) ion ([Au(tpy)Cl]2+) through X-ray radiolysis and optical excitation at a synchrotron. The original purpose of the experiment was to investigate the photoinduced structural changes of [Au(tpy)Cl]2+ upon 400 nm excitation using time-resolved X-ray liquidography (TRXL). Initially, the TRXL data did not show any signal that would suggest structural changes of the solute molecule, but after an induction time, the TRXL data started to show sharp peaks and valleys. In the early phase, AuNPs with two types of morphology, dendrites, and spheres, were formed by the reducing action of hydrated electrons generated by the X-ray radiolysis of water, thereby allowing the detection of TRXL data due to the laser-induced lattice expansion and relaxation of AuNPs. Along with the lattice expansion, the dendritic and spherical AuNPs were transformed into smaller, raspberry-shaped AuNPs of a relatively uniform size via ablation by the optical femtosecond laser pulse used for the TRXL experiment. Density functional theory calculations confirm that the reduction potential of the metal complex relative to the hydration potential of X-ray-generated electrons determines the facile AuNP formation observed for [Au(tpy)Cl]2+.

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As director Lee Chang-dong's film Burning (2018) has become a hot topic in terms of art, research on the work has also been conducted in various ways. However, this study attempted to examine the meaning of the movie <Burning>, focusing on 'sense', a discussion that has not been dealt with so far. Merlo-Ponti saw 'sense' as a basic step toward 'subjective body', and said that this sense and body are essential conditions for experiencing 'the world'. In other words, sense cannot be separated from the relationship between the body and the world, and eventually extends to the wide horizon of the world through the body as a subject. Accordingly, this study identified the elements of 'sense' in the movie <Burning> and analyzed how it combines with the world through the body as a subject. Furthermore, the possibility of what kind of performance the sensory experience can lead to for the audience was also considered.

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