Mid-infrared spectral evolution of amorphous magnesium silicate smokes annealed in vacuum: Comparison to cometary spectra
Mid-infrared spectral evolution of amorphous magnesium silicate smokes annealed in vacuum: Comparison to cometary spectra
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DOI：
10.1006/icar.1997.5854
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发表时间：
1998-01-01
期刊：
影响因子：
3.2
通讯作者：
Daukantas, PL
中科院分区：
文献类型：
--
作者：
Hallenbeck, SL;Nuth, JA;Daukantas, PL
采用气相冷凝法制备了无定形硅酸镁烟幕，并对其进行了真空退火处理。用红外光谱监测了样品随退火时间和温度的变化，重点研究了10微米硅酸盐特征的发展，初始凝聚物的红外光谱在9.3微米处出现了一个宽带，在1027K下热处理10.5h后，在9.8和11.0微米处出现了一个双极大值，在这段时间内，在下一次37.5FI的退火热处理中，10微米硅酸盐特征没有观察到明显的变化，此后随着样品的有序化，个别特征变得尖锐。这些样品的光谱演化在最初的混沌凝聚体和更有序的玻璃之间似乎有一个自然的停顿，光谱失速的持续时间从1000到1048它被研究并且高度依赖于退火温度。通过将观察到的谱带与位于8.35，9.00，9.77，10.87，11.30，11.87和12.22 PM的对称高斯峰进行拟合，对演变的10微米特征进行去卷积对硅酸铁和混合金属、镁-铁硅酸盐烟雾的初步研究结果表明，样品的演化速度明显不同。富含橄榄石的哈雷彗星、布拉德菲尔德彗星、利维彗星、穆勒彗星和海尔-波普彗星都具有发射特征，其双极大值分别为9.8和11.2微米，这与硅酸镁烟雾失速光谱非常相似。(C)1998年学术出版社。
Amorphous magnesium silicate smokes were prepared by vapor phase condensation and annealed in vacuum. The samples were monitored by IR spectroscopy as a function of annealing time and temperature, focusing on the development of the 10 mu m silicate feature, The IR spectrum of the initial condensate displayed a broad band at 9.3 mu m. After annealing for 10.5 h at 1027 K, a dual maximum was established at 9.8 and 11.0 mu m, Following this period of evolution no significant changes were observed in the 10 mu m silicate feature during the next 37.5 fi of annealing, Thereafter, individual features sharpened as the sample became more ordered. There appears to be a natural pause in the spectral evolution of these samples, midway between the initially chaotic condensate and the more ordered glass, The duration of the spectral stall was investigated from 1000 to 1048 It and was highly dependent on the annealing temperature, The evolving 10 mu m feature was deconvolved by fitting the observed bands with symmetric Gaussian peaks positioned at 8.35, 9.00, 9.77, 10.87, 11.30, 11.87, and 12.22 pm. Preliminary results of annealing studies on iron silicate and mixed-metal, magnesium-iron silicate smokes revealed distinctly different rates of sample evolution. The "olivine-rich" comets Halley, Bradfield, Levy, Mueller, and Hale-Bopp all display emission features with dual maxima at 9.8 and 11.2 mu m which closely resemble the magnesium silicate smoke stall spectra. (C) 1998 Academic Press.