2025-10-14 スウェーデン王立工科大学（KTH）
Web要約 の発言：
X-rays scattering off the valence electrons surrounding ammonia molecules (orange and green shapes) and getting captured on a detector. Photo: Ian Gabalski/Stanford/SLAC National Accelerator Laboratory
＜関連情報＞
- https://www.kth.se/en/om/nyheter/centrala-nyheter/forskare-har-lyckats-studera-reaktioner-pa-en-helt-ny-detaljniva-1.1430960
- https://journals.aps.org/prl/abstract/10.1103/53h3-vykl
硬X線散乱を用いた化学反応における価電子再配置の画像化 Imaging Valence Electron Rearrangement in a Chemical Reaction Using Hard X-Ray Scattering
Ian Gabalski, Alice Green, Philipp Lenzen, Felix Allum, Matthew Bain, Surjendu Bhattacharyya, Mathew A. Britton, Elio G. Champenois, Xinxin Cheng et al.
Physical Review Letters Published: 20 August, 2025
DOI: https://doi.org/10.1103/53h3-vykl
Abstract
We have observed the signatures of valence electron rearrangement in photoexcited ammonia using ultrafast hard x-ray scattering. Time-resolved x-ray scattering is a powerful tool for imaging structural dynamics in molecules because of the strong scattering from the core electrons localized near each nucleus. Such core-electron contributions generally dominate the differential scattering signal, masking any signatures of rearrangement in the chemically important valence electrons. Ammonia represents an exception to the typically high core-to-valence electron ratio. We measured 9.8 keV x-ray scattering from gas-phase deuterated ammonia following photoexcitation via a 200 nm pump pulse to the 3s Rydberg state. We observed changes in the recorded scattering patterns due to the initial photoexcitation and subsequent deuterium dissociation. Ab initio calculations confirm that the observed signal is sensitive to the rearrangement of the single photoexcited valence electron as well as the interplay between adiabatic and nonadiabatic dissociation channels. The use of ultrafast hard x-ray scattering to image the structural rearrangement of single valence electrons constitutes an important advance in tracking valence electronic structure in photoexcited atoms and molecules.
