Molybdenum disulfide (MoS2), a two-dimensional material purchased from SPI supplies, was analyzed using high-resolution X-ray photoelectron spectroscopy (XPS). A flake was mechanically exfoliated from a MoS2 bulk single crystal for the study. The XPS spectra of MoS2 obtained using monochromatic Al Kα radiation at 0.83401 nm include a survey scan, high-resolution spectra of O 1s, Mo 3p, C 1s, Mo 3d, S 2s, S 2p, Mo 4s, Mo 4p, S 3s, and valance band. Extended energy ranges were collected in the vicinity of the Mo 3d/S 2s, S 2p, and Mo 4s/Mo 4p/S 3s/Valence band regions allowing for fitting of surface plasmon features and determination of Tougaard scattering cross-section parameters. Quantitative analysis indicates a surface composition of MoS1.9.

A novel optical method has been developed for the measurement of thermal accommodation coefficients in the temperature-jump regime. The temperature dependence of the resonant frequency of a fused-silica microresonator's whispering-gallery mode is used to measure the rate at which the microresonator comes into thermal equilibrium with the ambient gas. The thermal relaxation time is related to the thermal conductivity of the gas under some simplifying assumptions and measuring this time as a function of gas pressure determines the thermal accommodation coefficient. Using a low-power tunable diode laser of wavelength around 1570 nm to probe a microsphere's whispering-gallery mode through tapered-fiber coupling, we have measured the accommodation coefficients of air, helium, and nitrogen on fused silica at room temperature. In addition, by applying thin-film coatings to the microsphere's surface, we have demonstrated that accommodation coefficients can be measured for various gases on a wide range of modified surfaces using this method.

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