Title
Infrared and Raman studies of hydroxide ions in NaCl extended to <tex>$H\rightarrow D$</tex> and <tex>$^{16}O\rightarrow^{18}O$</tex> isotope exchange
Author
Faculty/Department
Faculty of Sciences. Physics
Publication type
article
Publication
Lancaster, Pa ,
Subject
Physics
Source (journal)
Physical review: B
Physical review : B : condensed matter and materials physics. - Lancaster, Pa, 1998 - 2015
Volume/pages
63(2001) :13 , p. 1-13
ISSN
1098-0121
1550-235X
Article Reference
134301
Carrier
E-only publicatie
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
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.
Full text (open access)
https://repository.uantwerpen.be/docman/irua/a342c9/6784.pdf
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