Effect of Soft X-ray Irradiation on Film Properties of a Hydrogenated Si-Containing DLC Film.

The effect of soft X-ray irradiation on hydrogenated silicon-containing diamond-like carbon (Si-DLC) films intended for outer space applications was investigated by using synchrotron radiation (SR). We found that the reduction in film thickness was about 60 nm after 1600 mA·h SR exposure, whereas there was little change in their elemental composition. The reduction in volume was attributable to photoetching caused by SR, unlike the desorption of hydrogen in the case of exposure of hydrogenated DLC (H-DLC) film to soft X-rays. The ratio of the sp2 hybridization carbon and sp3 hybridization carbon in the hydrogenated Si-DLC films, sp2/(sp2 + sp3) ratio, increased rapidly from ~0.2 to ~0.5 for SR doses of less than 20 mA·h. SR exposure significantly changed the local structure of carbon atoms near the surface of the hydrogenated Si-DLC film. The rate of volume reduction in the irradiated hydrogenated Si-DLC film was 80 times less than that of the H-DLC film. Doping DLC film with Si thus suppresses the volume reduction caused by exposure to soft X-rays.

Performance of BL07A at NewSUBARU with installation of a new multi-layered-mirror monochromator.

Soft X-rays excite the inner shells of materials more efficiently than any other form of light. The investigation of synchrotron radiation (SR) processes using inner-shell excitation requires the beamline to supply a single-color and high-photon-flux light in the soft X-ray region. A new integrated computing multi-layered-mirror (MLM) monochromator was installed at beamline 07A (BL07A) of NewSUBARU, which has a 3 m undulator as a light source for irradiation experiments with high-photon-flux monochromatic light. The MLM monochromator has a high reflectivity index in the soft X-ray region; it eliminates unnecessary harmonic light from the undulator and lowers the temperature of the irradiated sample surfaces. The monochromator can be operated in a high vacuum, and three different mirror pairs are available for different experimental energy ranges; they can be exchanged without exposing the monochromator to the atmosphere. Measurements of the photon current of a photodiode on the sample stage indicated that the photon flux of the monochromatic beam was more than 1014 photons s-1 cm-2 in the energy range 80-400 eV and 1013 photons s-1 cm-2 in the energy range 400-800 eV. Thus, BL07A is capable of performing SR-stimulated process experiments.

Hybrid quantitative MRI using chemical shift displacement and recovery-based simultaneous water and lipid imaging: A preliminary study.

PURPOSE: To suppress olefinic signals and enable simultaneous and quantitative estimation of multiple functional parameters associated with water and lipid, we investigated a modified method using chemical shift displacement and recovery-based separation of lipid tissue (SPLIT) involving acquisitions with different inversion times (TIs), echo times (TEs), and b-values. MATERIALS AND METHODS: Single-shot diffusion echo-planar imaging (SSD-EPI) with multiple b-values (0-3000 s/mm2) was performed without fat suppression to separate water and lipid images using the chemical shift displacement of lipid signals in the phase-encoding direction. An inversion pulse (TI = 292 ms) was applied to SSD-EPI to remove olefinic signals. Consecutively, SSD-EPI (b = 0 s/mm2) was performed with TI = 0 ms and TE = 31.8 ms for T1 and T2 measurements, respectively. Under these conditions, transverse water and lipid images at the maximum diameter of the right calf were obtained in six healthy subjects. T1, T2, and the apparent diffusion coefficients (ADC) were then calculated for the tibialis anterior (TA), gastrocnemius (GM), and soleus (SL) muscles, tibialis bone marrow (TB), and subcutaneous fat (SF). Perfusion-related (D*) and restricted diffusion coefficients (D) were calculated for the muscles. Lastly, the lipid fractions (LF) of the muscles were determined after T1 and T2 corrections. RESULTS: The modified SPLIT method facilitated sufficient separation of water and lipid images of the calf, and the inversion pulse with TI of 292 ms effectively suppressed olefinic signals. All quantitative parameters obtained with the modified SPLIT method were found to be in general agreement with those previously reported in the literature. CONCLUSION: The modified SPLIT technique enabled sufficient suppression of olefinic signals and simultaneous acquisition of quantitative parameters including diffusion, perfusion, T1 and T2 relaxation times, and LF.

Enhancement of SERS background through charge transfer resonances on single crystal gold surfaces of various orientations.

Surface-enhanced Raman scattering (SERS) spectra are accompanied by broad background emission, which limits improvements in the signal-to-noise ratio. Despite the close correlation between the background generation and the SERS enhancement, the chemical origin of the background emission has remained somewhat mysterious. In this work, SERS spectra of organic monolayers are systematically measured on an atomically defined single crystalline gold surface of various orientations, which specifically define metal-molecule chemical interactions. The use of sphere-plane type plasmonic nanogap structures on a well-defined surface enables us to evaluate the contribution of charge transfer resonances to SERS enhancement. The present results not only reveal that charge transfer resonance at metal-molecule interfaces increases the intensity of plasmon-mediated broadband emission but also provide us a consistent view about electronic structures of metal-molecule interfaces.

Crystal face dependent chemical effects in surface-enhanced Raman scattering at atomically defined gold facets.

Among electromagnetic and chemical (CM) contributions to surface-enhanced Raman scattering (SERS), the former is becoming controllable according to the recent progress in nanofabrication of plasmonic metal structures. However, it is still difficult to control the latter effect. Here, the degree of each contribution to SERS signals is examined on well-defined single crystalline facets of gold by using optical field localization within sphere-plane type plasmonic cavities. Crystal face dependent SERS studies of aminobenzenthiol adsorbates clearly show the distinction between CM enhancements on different surfaces, suggesting that the CM-activity of "SERS-hotspots" is closely related to interfacial dipoles formed at metal-molecular junctions.