Lin Jung-Fu, Sturhahn Wolfgang, Zhao Jiyong, Shen Guoyin, Mao Ho-Kwang, Hemley Russell J
Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, N.W., Washington, DC 20015, USA.
Science. 2005 Jun 24;308(5730):1892-4. doi: 10.1126/science.1111724.
Sound velocities of hexagonal close-packed iron (hcp-Fe) were measured at pressures up to 73 gigapascals and at temperatures up to 1700 kelvin with nuclear inelastic x-ray scattering in a laser-heated diamond anvil cell. The compressional-wave velocities (VP) and shear-wave velocities (VS) of hcp-Fe decreased significantly with increasing temperature under moderately high pressures. VP and VS under high pressures and temperatures thus cannot be fitted to a linear relation, Birch's law, which has been used to extrapolate measured sound velocities to densities of iron in Earth's interior. This result means that there are more light elements in Earth's core than have been inferred from linear extrapolation at room temperature.
利用激光加热金刚石砧盒中的核非弹性X射线散射技术，在高达73吉帕斯卡的压力和高达1700开尔文的温度下测量了六方密排铁（hcp-Fe）的声速。在中等高压下，hcp-Fe的纵波速度（VP）和横波速度（VS）随温度升高而显著降低。因此，高压和高温下的VP和VS无法拟合到线性关系——Birch定律，该定律一直用于将测量的声速外推到地球内部铁的密度。这一结果意味着，地球核心中的轻元素比从室温下的线性外推推断出的要多。
