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Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals
Alkali halide single crystals are most commonly used as the diluent matrix in the tablet method or disk technique for spectroscopic measurements. However, stress-induced birefringence (SIB) of alkali halides as well as intrinsic birefringence manifest during the disk formation process. Thus, the tru...
Autores principales: | , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6017667/ https://www.ncbi.nlm.nih.gov/pubmed/29587395 http://dx.doi.org/10.3390/molecules23040757 |
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author | Ueno, Hiroki Arakane, Ryoga Matsumoto, Yoshihisa Tsumura, Tomoki Kitazaki, Akihito Takahashi, Toru Hirao, Shotaro Ohga, Yasushi Harada, Takunori |
author_facet | Ueno, Hiroki Arakane, Ryoga Matsumoto, Yoshihisa Tsumura, Tomoki Kitazaki, Akihito Takahashi, Toru Hirao, Shotaro Ohga, Yasushi Harada, Takunori |
author_sort | Ueno, Hiroki |
collection | PubMed |
description | Alkali halide single crystals are most commonly used as the diluent matrix in the tablet method or disk technique for spectroscopic measurements. However, stress-induced birefringence (SIB) of alkali halides as well as intrinsic birefringence manifest during the disk formation process. Thus, the true chiroptical measurement is disturbed by optical anisotropies (OA) containing SIB and intrinsic birefringence, except in the case of optical homogeneity. SIB is generally larger than intrinsic birefringence and has a value of several thousand millidegrees in the ultraviolet-visible wavelength range, although this varies with disk type. Here, to investigate the SIB origin, alkali halide crystals were examined using polarized light, X-ray diffraction, Fourier-transform infrared, and electron backscattering diffraction spectroscopic measurements. It was found that, after stress release, the SIB exhibited nonlinear long-time relaxation, which roughly converged within several hours, with the only time-invariant intrinsic birefringence remaining being due to OA. This behavior was strongly related to an increase in the quasi-amorphous domain and the generation of an air gap between the crystallite boundaries and their pellets. Further, a straightforward correlation was found between amorphization and an increase in the disk water content caused by deliquescence. Thus, the OA of alkali halide single crystals was found to have two different origins yielding intrinsic birefringence and SIB. |
format | Online Article Text |
id | pubmed-6017667 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-60176672018-11-13 Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals Ueno, Hiroki Arakane, Ryoga Matsumoto, Yoshihisa Tsumura, Tomoki Kitazaki, Akihito Takahashi, Toru Hirao, Shotaro Ohga, Yasushi Harada, Takunori Molecules Article Alkali halide single crystals are most commonly used as the diluent matrix in the tablet method or disk technique for spectroscopic measurements. However, stress-induced birefringence (SIB) of alkali halides as well as intrinsic birefringence manifest during the disk formation process. Thus, the true chiroptical measurement is disturbed by optical anisotropies (OA) containing SIB and intrinsic birefringence, except in the case of optical homogeneity. SIB is generally larger than intrinsic birefringence and has a value of several thousand millidegrees in the ultraviolet-visible wavelength range, although this varies with disk type. Here, to investigate the SIB origin, alkali halide crystals were examined using polarized light, X-ray diffraction, Fourier-transform infrared, and electron backscattering diffraction spectroscopic measurements. It was found that, after stress release, the SIB exhibited nonlinear long-time relaxation, which roughly converged within several hours, with the only time-invariant intrinsic birefringence remaining being due to OA. This behavior was strongly related to an increase in the quasi-amorphous domain and the generation of an air gap between the crystallite boundaries and their pellets. Further, a straightforward correlation was found between amorphization and an increase in the disk water content caused by deliquescence. Thus, the OA of alkali halide single crystals was found to have two different origins yielding intrinsic birefringence and SIB. MDPI 2018-03-25 /pmc/articles/PMC6017667/ /pubmed/29587395 http://dx.doi.org/10.3390/molecules23040757 Text en © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Ueno, Hiroki Arakane, Ryoga Matsumoto, Yoshihisa Tsumura, Tomoki Kitazaki, Akihito Takahashi, Toru Hirao, Shotaro Ohga, Yasushi Harada, Takunori Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals |
title | Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals |
title_full | Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals |
title_fullStr | Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals |
title_full_unstemmed | Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals |
title_short | Long-Time Relaxation of Stress-Induced Birefringence of Microcrystalline Alkali Halide Crystals |
title_sort | long-time relaxation of stress-induced birefringence of microcrystalline alkali halide crystals |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6017667/ https://www.ncbi.nlm.nih.gov/pubmed/29587395 http://dx.doi.org/10.3390/molecules23040757 |
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