Burnett, AD, Kendrick, J, Russell, C et al. (5 more authors) (2013) Effect of molecular size and particle shape on the terahertz absorption of a homologous series of tetraalkylammoniunn salts. Analytical Chemistry, 85 (16). 7926 - 7934. ISSN 0003-2700
Abstract
The absorption coefficient and refractive index have been measured for a homologous series of tetraalky-lammonium bromides over the frequency range 0.3− 5.5 THz. Spectral features are found to shift to lower frequencies as the molecular mass is increased ,asexpected.However,to understand the detailed structure of the observed spectral features, density functional perturbation theory calculations have been performed on the first four crystalline compounds in the series. From these calculations, we find that each spectrum is dominated by three translatory modes involving asymmetric motion of the ammonium cation and bromine counterion, although the overall number of active modes increases with increasing molecular size. The experimentally observed absorption is not completely described by the infrared active phonon modes alone. We show that it is also necessary to include the coupling of the phonon modes with the macroscopic field generated by the collective displacement of the vibrating ions, and we have applied an effective medium theory, which accounts for particle shape to allow for this effect in the calculation of the terahertz spectra.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Electronic & Electrical Engineering (Leeds) > Pollard Institute (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 13 Mar 2014 13:54 |
Last Modified: | 15 Sep 2014 01:47 |
Published Version: | http://dx.doi.org/10.1021/ac401657r |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/ac401657r |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:78038 |