Optical absorption and radiative heat transport in olivine at high temperature
Optical absorption and radiative heat transport in olivine at high temperature
复制标题
高温下橄榄石的光吸收和辐射热传输
DOI：
10.1029/jb084ib04p01603
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发表时间：
1979
影响因子：
--
通讯作者：
A. Duba
中科院分区：
文献类型：
--
作者：
T. Shankland;U. Nitsan;A. Duba
本文测量了天然橄榄石单晶和多晶（Mg/sub 1.84/Fe/sub 0.16/SiO/sub 4/）在300- 8000 nm波长范围内，温度300 - 1700 K，氧逸度在样品稳定范围内的吸收光谱。由于晶体场和多声子晶格振动吸收带的规则加宽，吸收随着温度的升高而显著增加;这些是辐射热传递所涉及的光谱区域中的主要吸收带。在这些带之间的“窗口”区，吸收系数从300 K时的接近零增加到1700 K时的约10- 15 cm/sup-1。在地幔条件下，由橄榄石单晶光谱计算的辐射热导率（K/sub R/）从300 K时的接近零增加到1700 K时的约5 × 10 - 3/ cal/cm·s·K（2 W/m·K），并且在800 K以上对温度的依赖性很弱。我们确定的K/sub R/比以前根据不同实验条件下的吸收测量的估计值低10- 20%。在多晶（纯橄榄岩）样品的传输大幅下降，温度循环，由于散射在不同的热膨胀产生的晶间界面。
The optical absorption spectra of natural single-crystal and polycrystalline olivine (mg/sub 1.84/Fe/sub 0.16/SiO/sub 4/) have been measured in the wavelength range 300--8000 nm at temperatures ranging from 300 to 1700 K and under oxygen fugacity well within the sample stability field. The absorption significantly increases with increasing temperature due to a regular broadening of both crystal field and multiphonon lattice vibrational absorption bands; these are the principal absorption bands in the spectral region involved in radiative heat transfer. In the 'window' region between these bands the absorption coefficient increases from near zero at 300 K to about 10--15 cm/sup -1/ at 1700 K. Under mantle conditions the radiative thermal conductivity (K/sub R/) calculated from the olivine single-crystal spectra increases from near zero at 300 K to about 5 x 10/sup -3/ cal/cm s K (2W/m K) at 1700 K and is only weakly dependent on temperature above 800 K. Our determination of K/sub R/ is 10--20% lower than previous estimates based on absorption measurements under different experimental conditions. In polycrystalline (dunite) samples the transmission decreased substantially with temperature cycling due to scattering at intergranular interfaces created by differential thermal expansion.