Abstract
There is an understandable desire to use simple unpolarized infrared analysis of unoriented anisotropic samples to extract quantitative information, rather than using more demanding polarized techniques. Owing to the fact that unpolarized infrared absorbance in birefringent media deviates from the Beer-Lambert law, previous studies have either warned against using unpolarized spectroscopy for quantitative purposes, or have used flawed error analysis to justify using simple averages of integrated absorbance of multiple absorbance bands as a proxy for total integrated polarized absorbance in the principal spectra. It is shown here that unpolarized infrared absorbance is correctly calculated by averaging in the transmission domain. The errors in estimates of principal absorbance by averaging of unpolarized absorbance spectra are evaluated using correct theory of unpolarized infrared transmission. Correction schemes for integrated absorbance based on linear-absorbance error calculations are shown to be inappropriate. A theory is developed that allows the sum of the polarized principal absorbance spectra to be estimated from multiple unpolarized measurements of randomly oriented samples. The systematic errors that arise when averaging in the absorbance domain are avoided by use of exact theory rather than an approximation. Numerical simulation shows that applying the new procedure to 10 unpolarized measurements of OH stretching bands in olivine results in convergence of the estimated total integrated principal polarized absorbance to within 10% of the true value for a sample size of 10 measurements, but the technique is limited to spectral regions that do not contain absorption bands that are simultaneously intensely absorbing and strongly anisotropic.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Highlight and Breakthrough. A fresh look at crystals in the Bishop Tuff
- Actinides in Geology, Energy, and the Environment. Remobilization of U and REE and the formation of secondary minerals in oxidized U deposits
- Actinides in Geology, Energy, and the Environment. Revision of the symmetry and the crystal structure of čejkaite, Na4(UO2)(CO3)3
- Characterization of ferric arsenate-sulfate compounds: Implications for arsenic control in refractory gold processing residues
- Crystal structure and chemistry of skarn-associated bismuthian vesuvianite
- Transformation of graphite to lonsdaleite and diamond in the Goalpara ureilite directly observed by TEM
- Quartz nanocrystals in the 2.48 Ga Dales Gorge banded iron formation of Hamersley, Western Australia: Evidence for a change from submarine to subaerial volcanism at the end of the Archean
- Synthesis and characterization of amphiboles along the tremolite–glaucophane join
- Elasticity of franklinite and trends for transition-metal oxide spinels
- Redox systematics of martian magmas with implications for magnetite stability
- Hydrogen incorporation and the oxidation state of iron in ringwoodite: A spectroscopic study
- Hydrous ringwoodite to 5 K and 35 GPa: Multiple hydrogen bonding sites resolved with FTIR spectroscopy
- Calibration of zircon as a Raman spectroscopic pressure sensor to high temperatures and application to water-silicate melt systems
- Computational study of the elastic behavior of the 2M1 muscovite-paragonite series
- Vanadium L2,3 XANES experiments and first-principles multielectron calculations: Impact of second-nearest neighboring cations on vanadium-bearing fresnoites
- A time-resolved X-ray diffraction study of Cs exchange into hexagonal H-birnessite
- Grain-boundary diffusion rates inferred from grain-size variations of quartz in metacherts from a contact aureole
- On the use of unpolarized infrared spectroscopy for quantitative analysis of absorbing species in birefringent crystals
- A computational model of cation ordering in the magnesioferrite-qandilite (MgFe2O4- Mg2TiO4) solid solution and its potential application to titanomagnetite (Fe3O4-Fe2TiO4)
- 3T-phlogopite from Kasenyi kamafugite (SW Uganda): EPMA, XPS, FTIR, and SCXRD study
- Revision of the crystal structure and chemical formula of haiweeite, Ca(UO2)2(Si5O12)(OH)2·6H2O
- Cation arrangement in the octahedral and tetrahedral sheets of cis-vacant polymorph of dioctahedral 2:1 phyllosilicates by quantum mechanical calculations
- High-pressure phase transitions of Fe3–xTixO4 solid solution up to 60 GPa correlated with electronic spin transition
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- The vibrational features of hydroxylapatite and type A carbonated apatite: A first principle contribution
- STEM investigation of exsolution lamellae and “c” reflections in Ca-rich dolomite from the Platteville Formation, western Wisconsin
- Karenwebberite, Na(Fe2+,Mn2+)PO4, a new member of the triphylite group from the Malpensata pegmatite, Lecco Province, Italy
- The crystal structure of ramdohrite, Pb5.9Fe0.1Mn0.1In0.1Cd0.2Ag2.8Sb10.8S24: A new refinement
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- Static disorders of atoms and experimental determination of Debye temperature in pyrope: Low- and high-temperature single-crystal X-ray diffraction study—Reply