To improve the primary density standard of the National Metrology Institute of Japan (NMIJ), the absolute densities of two 1 kg silicon spheres, NMIJ-S4 and NMIJ-S5, were determined by measuring their masses and volumes. The volumes of the two spheres were measured by optical interferometry based on the primary length standard of NMIJ. For the accurate volume determination, the thicknesses of the surface layers on the spheres were determined by x-ray photoelectron spectroscopy (XPS). By combining the results of optical interferometry and XPS, the volumes of the two spheres at 20.000 °C and 0 Pa were determined with relative standard uncertainties of 3.0 × 10 −8 and 2.9 × 10 −8 for NMIJ-S4 and NMIJ-S5, respectively. From these results, the sphere volumes at 20.000 °C and 101.325 kPa were determined using the isothermal compressibility of silicon. The masses of the spheres in air were determined based on the national prototype of the kilogram of Japan. From...

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绝对测量硅球的密度以提高NMIJ的初级密度标准

为了提高日本国家计量学会（NMIJ）的一次密度标准，通过测量质量和体积来确定两个1 kg的硅球NMIJ-S4和NMIJ-S5的绝对密度。基于NMIJ的基本长度标准，通过光学干涉法测量了两个球的体积。为了精确地确定体积，通过X射线光电子能谱（XPS）确定球体表面层的厚度。结合光学干涉和XPS的结果，确定了在20.000°C和0 Pa时两个球的体积，NMIJ-S4和NMIJ-S5的相对标准不确定度分别为3.0×10 -8和2.9×10 -8，分别。根据这些结果，使用硅的等温压缩率确定了在20.000°C和101.325 kPa下的球体积。空气中球体的质量是根据日本千克的国家原型确定的。从...