Shock-induced silicate vaporization: The role of electrons
Shock-induced silicate vaporization: The role of electrons
复制标题
冲击引起的硅酸盐蒸发：电子的作用
DOI：
10.1029/2011je004031
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Kodama R. and Matsui T.
中科院分区：
文献类型：
--
作者：
Kurosawa K.;Kadono T.;Sugita S.;Shigemori K.;Sakaiya T.;Hironaka Y;Ozaki N.;ShiroshitaA.,Cho Y.;Tachibana S.;Vinci T.;Ohno S.;Kodama R. and Matsui T.
我们对冲击加热的硅酸盐（透辉石）进行了光谱研究，并获得了光谱内容的时间演化，发射线的线宽，以及时间和辐照度平均峰值冲击温度。峰值冲击压力范围为330 - 760 GPa。时间分辨发射光谱表明，最初的光谱是黑体辐射;光谱演变为产生几条离子发射线，这些离子发射线又演变为在后期产生原子线。冲击加热的透辉石是高度解离和电离的，即使它很可能已经受到了接近液-汽相边界的高压条件。从离子到原子的光谱的时间演化强烈表明，电子复合发生在膨胀的冲击诱导的透辉石蒸气中。在大于330 GPa时的时间和辐照度平均峰值冲击温度低于理论Hugoniot曲线，具有恒定的等容比热，表明吸热冲击诱导电离。因此，我们得出结论，电子通过吸热冲击诱导的电离和随后的放热电子复合在能量分配中表现为重要的能量储存器。这种电子行为导致等熵释放后的蒸发程度更高，并且由于膨胀的冲击诱导硅酸盐蒸气中的放热电子复合而导致冷却速率比先前预期的更低。这些结果将影响行星科学中与超高速撞击事件相关的预测，例如月球的起源和化学反应以及撞击产生的硅酸盐蒸汽云中硅酸盐尘埃颗粒的产生。
We conducted a spectroscopic study of shock‐heated silicate (diopside) and obtained the time evolution of the spectral contents, the line widths of emission lines, and the time‐ and irradiance‐averaged peak shock temperatures. The peak shock pressures ranged from 330 to 760 GPa. Time‐resolved emission spectra indicated that the initial spectrum was blackbody radiation; the spectrum evolved to yield several ionic emission lines, which in turn evolved to yield atomic lines at the later stages. The shock‐heated diopside was highly dissociated and ionized, even though it is likely to have been subjected to high‐pressure conditions near the liquid–vapor phase boundary. The time evolution of the spectra, from ions to atoms, strongly suggests that electron recombination occurred in the expanding shock‐induced diopside vapor. The time‐ and irradiance‐averaged peak shock temperatures at >330 GPa were lower than the theoretical Hugoniot curve, with a constant isochoric specific heat, indicating endothermic shock‐induced ionization. Thus, we conclude that electrons behave as an important energy reservoir in energy partitioning via endothermic shock‐induced ionization and subsequent exothermic electron recombination. This electron behavior leads to a higher degree of vaporization after isentropic release and a lower cooling rate due to the exothermic electron recombination in expanding impact‐induced silicate vapors than previously expected. These results will affect the predictions associated with hypervelocity impact events in planetary science, such as the origin of the Moon and chemical reactions and production of silicate dust particles in impact‐generated silicate vapor clouds.