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Title: Measurement of the infrared optical constants for spectral modeling: n and k values for (NH4)2SO4 via single-angle reflectance and ellipsometric methods

Abstract

The optical constants n and k can be used to model infrared spectra, including refraction, absorption, reflectance, and emissivity, but obtaining reliable values for solid materials (pure or otherwise) presents a challenge: In the past, the best results for n and k have been obtained from bulk, homogeneous materials, free of defects. That is, materials where the Fresnel equations are operant since there is no light scattering. Since it is often not possible to obtain a pure macroscopic (crystalline) material, it may be possible to press the material into a (uniform, void-free) disk. We have recently been able to do this with ammonium sulfate powder and then measured the n & k values via two independent methods: 1) Ellipsometry - which measures the changes in amplitude and phase of light reflected from the material of interest as a function of wavelength and angle of incidence, and 2) Single angle specular reflectance with an FT spectrometer using a specular reflectance device within an FT instrument which measures the change in amplitude of light reflected from the material of interest as a function of wavelength and angle of incidence over a wide wavelength range. The quality of the derived n & kmore » values was tested by generating the reflectance spectra of the pellet and comparing to the calculated to measured reflectance spectra of the pure material which has been previously published. The comparison to literature values showed good accuracy and good agreement, indicating promise to measure other materials by such methods.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1358508
Report Number(s):
PNNL-SA-124897
DN2001000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XXIII, April 9, 2017, Anaheim, California. Proceedings of the SPIE, 10198:Article No. 101980J
Country of Publication:
United States
Language:
English
Subject:
Optical constants; index of refraction; specular reflectance; ellipsometry; ammonium sulfate; effective medium approximation

Citation Formats

Blake, Thomas A., Brauer, Carolyn S., Kelly-Gorham, Molly Rose K., Burton, Sarah D., Bliss, Mary, Myers, Tanya L., Johnson, Timothy J., and Tiwald, Thomas E.. Measurement of the infrared optical constants for spectral modeling: n and k values for (NH4)2SO4 via single-angle reflectance and ellipsometric methods. United States: N. p., 2017. Web. doi:10.1117/12.2264501.
Blake, Thomas A., Brauer, Carolyn S., Kelly-Gorham, Molly Rose K., Burton, Sarah D., Bliss, Mary, Myers, Tanya L., Johnson, Timothy J., & Tiwald, Thomas E.. Measurement of the infrared optical constants for spectral modeling: n and k values for (NH4)2SO4 via single-angle reflectance and ellipsometric methods. United States. doi:10.1117/12.2264501.
Blake, Thomas A., Brauer, Carolyn S., Kelly-Gorham, Molly Rose K., Burton, Sarah D., Bliss, Mary, Myers, Tanya L., Johnson, Timothy J., and Tiwald, Thomas E.. Fri . "Measurement of the infrared optical constants for spectral modeling: n and k values for (NH4)2SO4 via single-angle reflectance and ellipsometric methods". United States. doi:10.1117/12.2264501.
@article{osti_1358508,
title = {Measurement of the infrared optical constants for spectral modeling: n and k values for (NH4)2SO4 via single-angle reflectance and ellipsometric methods},
author = {Blake, Thomas A. and Brauer, Carolyn S. and Kelly-Gorham, Molly Rose K. and Burton, Sarah D. and Bliss, Mary and Myers, Tanya L. and Johnson, Timothy J. and Tiwald, Thomas E.},
abstractNote = {The optical constants n and k can be used to model infrared spectra, including refraction, absorption, reflectance, and emissivity, but obtaining reliable values for solid materials (pure or otherwise) presents a challenge: In the past, the best results for n and k have been obtained from bulk, homogeneous materials, free of defects. That is, materials where the Fresnel equations are operant since there is no light scattering. Since it is often not possible to obtain a pure macroscopic (crystalline) material, it may be possible to press the material into a (uniform, void-free) disk. We have recently been able to do this with ammonium sulfate powder and then measured the n & k values via two independent methods: 1) Ellipsometry - which measures the changes in amplitude and phase of light reflected from the material of interest as a function of wavelength and angle of incidence, and 2) Single angle specular reflectance with an FT spectrometer using a specular reflectance device within an FT instrument which measures the change in amplitude of light reflected from the material of interest as a function of wavelength and angle of incidence over a wide wavelength range. The quality of the derived n & k values was tested by generating the reflectance spectra of the pellet and comparing to the calculated to measured reflectance spectra of the pure material which has been previously published. The comparison to literature values showed good accuracy and good agreement, indicating promise to measure other materials by such methods.},
doi = {10.1117/12.2264501},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri May 05 00:00:00 EDT 2017},
month = {Fri May 05 00:00:00 EDT 2017}
}

Conference:
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