Funamori Nobumasa, Kojima Kenji M, Wakabayashi Daisuke, Sato Tomoko, Taniguchi Takashi, Nishiyama Norimasa, Irifune Tetsuo, Tomono Dai, Matsuzaki Teiichiro, Miyazaki Masanori, Hiraishi Masatoshi, Koda Akihiro, Kadono Ryosuke
Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan.
Muon Science Laboratory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan.
Sci Rep. 2015 Feb 13;5:8437. doi: 10.1038/srep08437.
Hydrogen in the Earth's deep interior has been thought to exist as a hydroxyl group in high-pressure minerals. We present Muon Spin Rotation experiments on SiO2 stishovite, which is an archetypal high-pressure mineral. Positive muon (which can be considered as a light isotope of proton) implanted in stishovite was found to capture electron to form muonium (corresponding to neutral hydrogen). The hyperfine-coupling parameter and the relaxation rate of spin polarization of muonium in stishovite were measured to be very large, suggesting that muonium is squeezed in small and anisotropic interstitial voids without binding to silicon or oxygen. These results imply that hydrogen may also exist in the form of neutral atomic hydrogen in the deep mantle.
地球深部内部的氢一直被认为以高压矿物中的羟基形式存在。我们对二氧化硅斯石英进行了μ子自旋旋转实验，斯石英是一种典型的高压矿物。发现注入斯石英中的正μ子（可被视为质子的轻同位素）捕获电子形成μ介子（对应于中性氢）。测量得到斯石英中μ介子的超精细耦合参数和自旋极化弛豫率非常大，这表明μ介子被挤压在小的各向异性间隙空隙中，且不与硅或氧结合。这些结果意味着氢在深部地幔中也可能以中性原子氢的形式存在。
