1. Status of Beamline BL07LSU at SPring-8
As described in the Preface, the University-of-Tokyo high-brilliance synchrotron soft
X-ray outstation beamline BL07LSU at SPring-8 was maintained until the first half of2022 by the permanent staff members with adjuncts for user operations for the purposeof promoting advanced spectroscopy of solid and soft (including bio-) materials, andvarious joint-research experiments were conducted by both staff and users in the G-type(general), S-type (special), and P-type (priority) applications. Here, the activities at theambient pressure X-ray photoemission spectroscopy, soft X-ray spectroscopic imaging,
3D-scanning photoelectron microscope (3D nano-ESCA) and high-resolution soft X-rayemission spectroscopy (HORNET) stations until the first half of 2022, and developmentof soft X-ray spectroscopic imaging station through collaboration with RIKEN from thesecond half of 2022, are briefly described below.
(1) Ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)
AP-XPS station is aimed for operando chemical analysis during catalytic reactions at
the gas/solid interface to unveil the reaction mechanism. The AP-XPS system is equippedwith a differentially pumped electron analyzer (SPECS, PHOIBOS 150 NAP) and an
ambient pressure gas cell. XPS measurements can be performed both under ultrahighvacuum and in gas pressure up to 100 mbar. Reactant and product molecules of a catalytic
reaction are monitored by mass spectroscopy and, simultaneously, chemical states of thereaction intermediates at a surface are directly examined by AP-XPS.
A variety of research projects has been conducted at the AP-XPS station. In 2022,
issues at the atomic sheet were focused and the functionalities, such as sensing andreaction, were investigated.
(2) Soft X-ray imaging
We developed a new soft X-ray microscopy system named CARROT (CoherentAchromatic Rotational Reflective Optics for pTychography) in 2021. CARROT canrealize high-resolution and high-sensitivity soft X-ray imaging by utilizing the coherent
property of BL07LSU. The CARROT system with a total reflection Wolter mirror
achieved a resolution of about 50 nm in a test chart evaluation. We have also shown that
it is possible to visualize the magnetic domain structures of an ultrathin metal film using
X-ray magnetic circular dichroism.
We also demonstrate the potential of applying CARROT to cell biology by measuringdrug-treated mammalian cells. Various changes in the cell body were observed using soft
X-ray imaging at 50 nm resolution.

(3) 3D-scanning photoelectron microscope (3D-nanoESCA)
3D-nanoESCA can be used for sub-100 nm range microscopic 2D mapping and depth
profile of the chemical structure of functional materials and devices. In 2022, twosignificant experiments were performed. 2D electronic mappings of P-type and N-typealloyed thermoelectric materials (FAST) composed of safe, durable, and inexpensive Fe,Al, and Si elements developed by Dr. Takagiwa were obtained and compared and the ptype sample showed a peak shift to the lower binding energy for both Fe 2p, Al 2p, andSi 2p, and the shift of the chemical potential was quantitatively determined. The shapedifference was also detected in the valence spectra, suggesting that the intra-gap position
has an effect. Dr. Zhang obtained Ti 2p 2D photoelectron images of TiO2 (anatase)particles with different facet surfaces, showing the existence of a space-charge layer ofabout 40 nm between the interfaces of the two facets. Photogenerated electrons and holes
are expected to accumulate in the (101) and (001) facets, respectively, enhancing thephotocatalytic activity.
(4) Ultra high-resolution soft X-ray emission spectroscopy (HORNET)
The station is dedicated for soft X-ray emission (or resonant inelastic X-ray scattering:RIXS) spectroscopy measurements with high-resolution (E/ΔE > 10,000) and undervarious environmental conditions (gas, liquid, and solid). In 2022, 11 studies wereperformed. Among them, the studies by Profs. Y. Higaki and S. Horiuchi, and Dr. Y.
Hashikawa were performed under the Grant-in-Aid for Scientific Research New Science
Project and targeted water at various interfaces; in concentrated polymer, within porous
crystals, and encapsulated in fullerenes. Other works include secondary battery electrodes
and catalysts for water electrolysis, aiming for the improved performance of them. Dr.
Fujino et al. explored d/π-conjugated molecules in water and detected changes in the Ni
3d electronic states due to altered intermolecular interactions in film states upon heating.
All these studies are quite advanced for operando RIXS measurements, and they willcollectively advance our technique and suggest the possibility of practical applications in
the future experiments at NanoTerasu.