Near‐infrared optical constants of naturally occurring olivine and synthetic pyroxene as a function of mineral composition
Near‐infrared optical constants of naturally occurring olivine and synthetic pyroxene as a function of mineral composition
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天然橄榄石和合成辉石的近红外光学常数与矿物成分的函数关系
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发表时间：
2013
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通讯作者：
P. Isaacson
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作者：
D. Trang;P. Lucey;J. Gillis;J. Cahill;R. Klima;P. Isaacson
辐射转移理论将有助于确定橄榄石和辉石的比例和成分从行星体的表面组成的密切混合的矿物。为了使用辐射传递技术，该模型需要橄榄石和辉石的光学常数。光学常数是描述光在介质中被吸收（k）和折射（n）的程度的参数。在这里，我们仅在近红外范围内对天然橄榄石的0.6至2.5 µm进行参数化，作为镁橄榄石数和合成辉石相对于硅灰石和硅铁石数的函数。与以前的工作相比，这项研究是对以前工作的改进，因为我们有一个多样化和更大的样本量，导致强大的光学参数。此外，我们用修改的高斯模型（MGM）来表征每个k谱。MGM是一个物理上真实的近红外电子跃迁模型。在每个光谱中，我们分别用高斯函数和线性函数的逆函数对每个吸收和连续谱进行建模。我们发现，我们的拟合程序以稳健和一致的方式表征橄榄石和辉石的k谱。然后，我们使用回归分析来表征高斯和连续体的每个参数作为矿物成分的函数。从这项工作中开发的光学参数将允许使用来自Dawn，MESSENGER，SELENE和Chandrayaan-1等任务的数据计算行星表面的矿物比例和成分。
Radiative transfer theory will assist in determining olivine and pyroxene proportions and compositions from the surface of a planetary body composed of intimately mixed minerals. In order to use radiative transfer techniques, the model requires the optical constants of olivine and pyroxene. Optical constants are parameters that describe the degree light absorbed (k) and refracted (n) in a medium. Here we only parameterize k in the near infrared from 0.6 to 2.5 µm of natural olivine as a function of forsterite number and synthetic pyroxene with respect to wollastonite and ferrosilite number. In contrast to previous work, this study is an improvement on previous work because we have a diverse and larger sample size leading to robust optical parameters. Additionally, we characterize each k‐spectrum with the modified Gaussian model (MGM). MGM is a physically realistic model of near‐infrared absorptions due to electronic transitions. In each spectrum, we model each absorption and continuum with Gaussians and an inverse of a linear function, respectively. We find that our fitting routine characterizes the olivine and pyroxene k‐spectra in a robust and consistent manner. Then we use regression analysis to characterize each parameter of the Gaussians and the continuum as a function of mineral composition. The developed optical parameters from this work will allow calculations of mineral proportions and compositions on planetary surfaces with use of data from missions such as Dawn, MESSENGER, SELENE, and Chandrayaan‐1.