X-ray scattering data from Norway spruce at different moisture conditions

This data includes small and wide-angle X-ray scattering (SAXS, WAXS) intensities measured for Norway spruce (Picea abies) wood.

The experiments were done in perpendicular transmission geometry, with the wood fiber axis roughly vertical and the radial direction of the wood tissue parallel to the X-ray beam, using a Xenocs Xeuss 3.0 C SAXS/WAXS device and Cu K-alpha radiation (wavelength 1.542 Å). The scattering patterns were recorded using an EIGER2 R 1M detector (pixel size 75 µm). The wood sample was measured first in wet state (saturated with water; "Wet"), and then equilibrated at different relative humidities (RH) in the following order: 95% ("RH95_1st"), 85% ("RH85"), 70% ("RH70"), 50% ("RH50_1st"), 20% ("RH20"), 10% ("RH10"), 50% ("RH50_2nd"), 95% ("RH95_2nd"). The sample-to-detector distance was 0.4139 m in SAXS, and 0.1528 m for the first 4 conditions (until "RH70") and 0.1525 m for the remaining 5 conditions in WAXS. Beam center (in detector pixels) was at x=540.6, y=667.0 (except y=635.0 in "RH70") in SAXS and x=1540, y=1521 in WAXS.

For each of the 9 moisture conditions, files corresponding to 3 different processing steps are provided:

• "_bgsub_saxs.txt" and "_bgsub_waxs.txt" are ASCII files that contain the normalized and background-subtracted detector images (intensity in units mm^-1) corresponding to SAXS and WAXS, respectively. Pixels to be masked have the value "nan".
• "_bgsub_saxs_pol90.txt" and "_bgsub_waxs_pol90.txt" contain azimuthally regrouped images (90 bins in azimuthal angle) based on "_bgsub_saxs.txt" and "_bgsub_waxs.txt", respectively. PNG image files "_bgsub_saxs_pol.png" and "_bgsub_waxs_pol.png" are provided for reference.
• "_bgsub_pol90_ibg.txt" and "_bgsub_waxs_pol90_vert_ibg.txt" contain the equatorial and meridional anisotropic intensities, respectively, which were obtained from the azimuthally regrouped images by subtracting the isotropic scattering from the equatorial or meridional intensity (sector width 25°) at each value of the scattering vector q. The equatorial anisotropic intensities from SAXS and WAXS were merged by scaling the SAXS intensity, and the meridional anisotropic intensity is provided for the WAXS range only. The files contain columns for the magnitude of the scattering vector (q, unit Å^-1), anisotropic intensity (I_ani, unit mm^-1), error of anisotropic intensity (dI_ani, unit mm^-1), and isotropic intensity (I_iso, unit mm^-1).

More detailed descriptions of the sample, the measurement, and the data processing can be found in the following reference:
Antti Paajanen, Aleksi Zitting, Lauri Rautkari, Jukka A. Ketoja, Paavo A. Penttilä. Nanoscale mechanism of moisture-induced swelling in wood microfibril bundles. Nano Letters 2022, 22(13): 5143–5150, DOI: 10.1021/acs.nanolett.2c00822