Journal Article Increase of the emission of laser-produced plasmas under N2 gas atmosphere in the 2.9 – 6 nm region

加道, 雅孝  ,  岸本, 牧  ,  江島, 丈雄  ,  篠原, 邦夫

111pp.054102-1 - 054102-4 , 2017-07 , American Institute of Physics
The wavelength region between the K-edges of carbon and oxygen is termed as the water window (= 2.3 – 4.5 nm) and is considered to be suitable for the observation of nanometer-scale structures composed of light elements in an aqueous solution because of both the short wavelength and transparency of the light. The nanometer-scale structures in an aqueous solution fluctuate owing to Brownian motion. Therefore, the observation of the nanometer-scale structures can be achieved by one-shot exposure of the light in the water window. To observe the nanometer-scale structures by the one-shot exposure, the light source of the microscope working in the water window should exhibit a high light-flux. One of the light sources used for the one-shot exposure is the laser-produced plasma (LPP) light source. The conversion efficiency of the LPP light source in the water window is 1% or less. Therefore, a high intensity laser or improvement of the conversion efficiency is required for the one-shot observation. In this study, an emission-intensity increase of an LPP light source is observed in the wavelength region from 2.9 nm to 6 nm under a N2 gas atmosphere. The intensity value, calibrated by the gas absorbance, was increased up to 5 times in proportion to the N2 pressure, which was increased from 0.0 Torr to 3.0 Torr. Experimental conditions demonstrate that the conversion efficiency of the LPP light source is improved by the introduction of gas.

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