X-ray tomography is a powerful method for visualizing the three-dimensional structure of an object with a high spatial resolution. Conventional time-resolved x-ray tomography using synchrotron radiation requires fast rotation of the object, which limits the temporal resolution and hampers its application to, e.g., fluids and in vivo observation of living beings. Here, we present a multibeam x-ray optical system for high-speed 4D tomography, which can obtain projection images of a sample in a wide angular range simultaneously. It consists of about three dozen single-crystalline blades oriented with different angles to the incident beam, which each Bragg-reflect a part of the incident x-rays in the direction of the sample position. Thirty-two projection images covering an angular range of more than ± 70 ∘ were obtained without moving the sample or optical system, with an exposure time of 1 ms. The data set was successfully used for reconstructing the three-dimensional structure of two test samples. The optical system provides the basis for realizing millisecond time resolution x-ray tomography of nonrepeatable phenomena, and can be expected to be useful for other applications as well, for example, for time-resolved element-specific imaging.

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The surface structural change of the rutile–TiO2(110) during the UV-light-induced wettability conversion was studied with atomic resolution using the X-ray crystal truncation rod (CTR) scattering method. We confirmed that an atomic-scale surface structural change occurs during the UV-light irradiation by using time-resolved CTR profile measurements. Quantitative structural analysis on static CTR data, which were measured before and after the conversion, shows that on the hydrophobic (nonphotoirradiated) surface the five-coordinated Ti atom is covered with an O atom likely in a form of water molecule, for which the bridging O atom is not likely hydroxylated, and that large atomic positional fluctuations occur on the hydrophilic (photoirradiated) surface possibly due to the photoinduced proton transfer from the intact water molecule to the bridging oxygen atom. The resulting surface OH groups might be active sites for water adsorption to make the surface superhydrophilic.

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