A semi-classical model of proton tunnelling in hydrogen-bonded compounds

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dc.contributor.advisorRobertson, G Nen_ZA
dc.contributor.authorLawrence, Michael Colinen_ZA
dc.date.accessioned2016-03-11T14:28:38Z
dc.date.available2016-03-11T14:28:38Z
dc.date.issued1980en_ZA
dc.descriptionBibliography: pages 233-238.en_ZA
dc.description.abstractTwo back-to-back Morse potentials are used to model the protonic potential in a hydrogen bond. A mathematical method is developed to obtain semi-classical solutions for the eigenvalues and eigenfunctions of the potential. Particular care is taken over the form of approximation used in the vicinity of the barrier top. The double Morse potential is then used as the fundamental element in the analysis of the proton dynamics in a number of hydrogen-bonded species: a) Chromous acid. A consistent, quantitative explanation is found for the νs(OH)/vs(OD) bands in the mid-infrared spectra of CrOOH/CrOOD. The 226 cm⁻¹ band in the far infrared and neutron scattering spectra of CrOOH is shown to be caused by the protonic tunnelling mode. b) Carboxylic and Dicarboxylic acids. The 140 cm⁻¹ protonic upper state splitting in dimeric formic acid proposed by Excoffon and Marechal (1972) is shown to be supported by the double Morse potential analysis. The analysis suggest's however that the two hydrogen-bonded protons in (HCOOH)₂ tunnel independently. The anomalous vs(OH)/vs(OD) intensity ratios observed in the infrared spectra of both adipic acid and dimeric formic acid could not be explained in terms of mechanical anharmonicity alone. The protonic tunnelling frequency in crystalline formic acid is shown to be about 23 cm⁻¹ , which supports the order-disorder interpretation of the observed phase transition in this crystal. c) Potassium Dihydrogen Phosphate (KDP). The crystallographic and infrared spectroscopic data for KDP and DKDP are interpreted consistently using the double Norse potential. The bare single-particle tunnelling frequency Ω is estimated to be 320 ± 10 cm⁻¹ and the overtone band at 4600 cm⁻¹ in the infrared spectrum of KDP is shown to be a :0 →:3> single particle transition. The model is capable of predicting the temperature and pressure dependence of both the protonic tunnelling frequency and the protonic inter-site separation δ. The soft-mode Raman data of Peercy (1975) is re-analysed allowing for the temperature dependence of Ω.en_ZA
dc.identifier.apacitationLawrence, M. C. (1980). <i>A semi-classical model of proton tunnelling in hydrogen-bonded compounds</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Physics. Retrieved from http://hdl.handle.net/11427/17663en_ZA
dc.identifier.chicagocitationLawrence, Michael Colin. <i>"A semi-classical model of proton tunnelling in hydrogen-bonded compounds."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Physics, 1980. http://hdl.handle.net/11427/17663en_ZA
dc.identifier.citationLawrence, M. 1980. A semi-classical model of proton tunnelling in hydrogen-bonded compounds. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Lawrence, Michael Colin AB - Two back-to-back Morse potentials are used to model the protonic potential in a hydrogen bond. A mathematical method is developed to obtain semi-classical solutions for the eigenvalues and eigenfunctions of the potential. Particular care is taken over the form of approximation used in the vicinity of the barrier top. The double Morse potential is then used as the fundamental element in the analysis of the proton dynamics in a number of hydrogen-bonded species: a) Chromous acid. A consistent, quantitative explanation is found for the νs(OH)/vs(OD) bands in the mid-infrared spectra of CrOOH/CrOOD. The 226 cm⁻¹ band in the far infrared and neutron scattering spectra of CrOOH is shown to be caused by the protonic tunnelling mode. b) Carboxylic and Dicarboxylic acids. The 140 cm⁻¹ protonic upper state splitting in dimeric formic acid proposed by Excoffon and Marechal (1972) is shown to be supported by the double Morse potential analysis. The analysis suggest's however that the two hydrogen-bonded protons in (HCOOH)₂ tunnel independently. The anomalous vs(OH)/vs(OD) intensity ratios observed in the infrared spectra of both adipic acid and dimeric formic acid could not be explained in terms of mechanical anharmonicity alone. The protonic tunnelling frequency in crystalline formic acid is shown to be about 23 cm⁻¹ , which supports the order-disorder interpretation of the observed phase transition in this crystal. c) Potassium Dihydrogen Phosphate (KDP). The crystallographic and infrared spectroscopic data for KDP and DKDP are interpreted consistently using the double Norse potential. The bare single-particle tunnelling frequency Ω is estimated to be 320 ± 10 cm⁻¹ and the overtone band at 4600 cm⁻¹ in the infrared spectrum of KDP is shown to be a :0 →:3> single particle transition. The model is capable of predicting the temperature and pressure dependence of both the protonic tunnelling frequency and the protonic inter-site separation δ. The soft-mode Raman data of Peercy (1975) is re-analysed allowing for the temperature dependence of Ω. DA - 1980 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1980 T1 - A semi-classical model of proton tunnelling in hydrogen-bonded compounds TI - A semi-classical model of proton tunnelling in hydrogen-bonded compounds UR - http://hdl.handle.net/11427/17663 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/17663
dc.identifier.vancouvercitationLawrence MC. A semi-classical model of proton tunnelling in hydrogen-bonded compounds. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Physics, 1980 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/17663en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Physicsen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherPhysicsen_ZA
dc.titleA semi-classical model of proton tunnelling in hydrogen-bonded compoundsen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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