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Title
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Infrared and Raman studies of hydroxide ions in NaCl extended to and isotope exchange
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Author
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Abstract
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| Substitutional OH- and OD- defects in NaCl have been studied with Fourier-transform infrared (FTIR) and polarized Raman-scattering (RS) spectroscopy. For the first time, the motional levels of the OH- were clearly resolved in their stretch-mode (SM) absorption spectra, showing no change in splitting under (OH-)-O-16 --> (OH-)-O-18 isotope exchange. Due to extremely small oscillator strengths, the first harmonic SM absorptions of (OD-)-O-16 and (OD-)-O-18 defects were not detectable. In contrast to this, the almost equal RS strengths of OH- and OD- defects permitted their detailed comparative investigation with polarized Raman scattering. The resulting low-frequency motional levels of OD- in both ground and excited SM states are found to be quite different from those of OH- and are hard to reconcile with some of the existing models. A reasonably good fit of the OH- and OD- data can be achieved with a simple V-4 Devonshire model; this suggests hindered rotation of a strongly off-center shifted center of mass in a potential with smaller energy barriers for OD- compared to OH-. Despite the unexplained weakness of the first harmonic SM absorption of OD-, phonon and librational sidebands are observed with almost similar strength as those of OH-. Their symmetry was determined by polarized RS and/or FTIR absorption measurements under uniaxial stress alignment. The "normal" OH-/OD- isotope shift of the librational sideband and the observation of its second harmonic show that this angular motion occurs around the center of mass in a strong and nearly harmonic potential. |
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Language
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English
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Source (journal)
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Physical review : B : condensed matter. - New York, N.Y., 1978 - 1997
Physical review : B : condensed matter and materials physics. - Lancaster, Pa, 1998 - 2015
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Publication
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New York, N.Y.
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2001
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ISSN
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0163-1829
[print]
1095-3795
[online]
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DOI
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10.1103/PHYSREVB.63.134301
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Volume/pages
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63
:13
(2001)
, p. 1-13
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Article Reference
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134301
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ISI
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000167895000048
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Medium
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E-only publicatie
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Full text (Publisher's DOI)
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Full text (open access)
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