(a) Photograph of the reactor showing the sample position, general layout, mounting rails, and gas and electrical connections. (b) Exploded view of the reactor showing the x-ray direction and individual components numbered as follows: 1: retainer ring, 2: circuit board containing relative humidity sensor, 3: o-ring, 4: reactor body, 5: mounting plate, 6: o-ring, and 7: sample plate.
Schematic showing the layout of the different layers in the PCB which contains the RH/T sensor. P1 is the RH/T sensor, P2 is the electrical connection receptacle, and C1 is a 0.1 μF capacitor. Parts P2 and C1 attach to the top of the PCB, while part P1 attaches to the bottom (the “P1” label on the figure is printed as a mirror image for this reason) and is exposed to the process gas flow in the reactor.
Focusing scheme and spatial considerations between the elements inside the microscope. The distance between the sample and the order sorting aperture (A0) depends on the specific zone plate and x-ray energy used, but is typically on the order of 300 μm at the carbon K absorption edge.
Cartoon showing the relationship between the sample thickness, t, and A0 when using the in situ reactor. To maintain focus while filtering higher order contamination from the x-ray beam, t should be less than the smallest optimum A0 value for the energies of interest with a specific zone plate.
Illustration showing the sample plates in detail. On plate (a) the sample mounts to the exterior of the plate. The sample mounts to the interior of plate (b).
Schematic showing the plumbing and connections to deliver the humidified gas flow to the reactor inside the STXM chamber.
A series of 6 μm × 6 μm STXM images and oxygen maps of the same set of NaCl particles while the RH increased through the deliquescence relative humidity (DRH) point of 75%. (a) 540 eV image of NaCl particles at 9% RH. (b) Oxygen map of the same region as (a), also at 9% RH. (c) Oxygen map of the same particles at 73.6% RH. (d) Oxygen map of the same particles at 74.3% RH. A clear deliquescence event occurred between (c) and (d). The colorbar to the right of the figure displays the optical density values of (b)–(d).
Measured deliquescence relative humidity (DRH) values (according to the enclosed RH/T sensor in the reactor) versus the tabulated literature values of DRH for the four different salts used for calibration. 21 The line represents a linear fit to the four data points.
X-ray absorption spectra across the oxygen K-edge taken through two Si3N4 windows at dry conditions and at a RH of 92.5% using the in situ reactor (a) and while filling the entire STXM chamber with water vapor (b). For direct comparison of the two cases, plot (c) shows the normalized absorption spectra for the water vapor along the optical path in units of optical density for the two scenarios.
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