dc.contributor.advisor Graham, W. R. M. dc.contributor.author Presilla-Márquez, José-Domingo en_US dc.date.accessioned 2019-10-11T15:11:14Z dc.date.available 2019-10-11T15:11:14Z dc.date.created 1992 en_US dc.date.issued 1992 en_US dc.identifier aleph-569010 en_US dc.identifier Microfilm Diss. 587. en_US dc.identifier.uri https://repository.tcu.edu/handle/116099117/34216 dc.description.abstract Fourier transform studies of silicon-carbon clusters produced by vaporizing mixtures of silicon and carbon-12 or carbon-13 and quenching the products in argon, have enabled the identification of new vibrational spectra and structures. The far infrared $\nu\sb3(b\sb2)$ fundamental has been found at 160.4 cm$\sp{-1}$ for SiC$\sb2$. Its structure is now described as T-shaped with ionic bonding. In the case of Si$\sb2$C, a previously observed vibration at 1188.4 cm$\sp{-1}$ has been confirmed as the $\nu\sb3(b\sb2)$, antisymmetric Si-C stretching mode, and a new vibration at 839.5 cm$\sp{-1}$ has been identified as the $\nu\sb1(a\sb1)$, symmetric Si-Si stretching fundamental. The $\nu\sb2(a\sb1)$ bending mode has not been observed; however, the $\nu\sb2(a\sb1)$ + $\nu\sb3(b\sb2)$ combination band has been identified at 1354.8 cm$\sp{-1}$. The results of force constant adjustment calculations confirm the ground state geometry of Si$\sb2$C as a floppy, bent symmetrical structure. Five out of six fundamental modes have been identified for the Si$\sb3$C cluster which is observed here for the first time: the symmetric breathing vibration, $\nu\sb1(a\sb1)$ = 658.2 cm$\sp{-1}$; the Si$\sb\beta$-Si$\sb\alpha$-Si$\sb\beta$ symmetric deformation vibration, $\nu\sb2(a\sb1)$ = 511.8 cm$\sp{-1}$; the Si$\beta$-C-Si$\sb{\beta}$ symmetric deformation vibration, $\nu\sb3(a\sb1)$ = 309.5 cm$\sp{-1}$; the Si$\sb\beta$-C antisymmetric stretching vibration, $\nu\sb5(b\sb2)$ = 1101.4 cm$\sp{-1}$; and the Si$\sb\alpha$-Si$\sb\beta$ antisymmetric stretching vibration, $\nu\sb6(b\sb2)$ = 357.6 cm$\sp{-1}$. The fundamental frequencies, relative intensities, and isotopic shifts are in excellent agreement with the results of ab initio calculations predicting a rhomboidal structure of $C\sb{2v}$ symmetry for Si$\sb3$C, with carbon-silicon transannular bonding between the two equivalent Si atoms. Another new silicon-carbon cluster, rhombic Si$\sb2$C$\sb2$, has been identified and the $\nu\sb3(b\sb{\rm 1u})$ = 982.9 and $\nu\sb4(b\sb{\rm 2u})$ = 382.2 cm$\sp{-1}$ fundamentals have been assigned. These results are in excellent agreement with ab initio calculations. The first assignment of vibrational fundamentals for linear centrosymmetric Si$\sb2$C$\sb3$: the C=C stretching mode, $\nu\sb3(\sigma\sb{u})$ = 1955.2 cm$\sp{-1}$, and the Si-C stretching mode $\nu\sb4(\sigma\sb{u})$ = 898.9 cm$\sp{-1}$, has been made. These results are again in agreement with ab initio calculations. The discovery of new spectra and structures for a large number of silicon-carbon clusters has been achieved through comprehensive experimental measurements of isotopic shifts and relative intensities, and a productive interplay with ab initio theory. dc.format.extent xiii, 111 leaves : illustrations en_US dc.format.medium Format: Print en_US dc.language.iso eng en_US dc.relation.ispartof Texas Christian University dissertation en_US dc.relation.ispartof AS38.P732 en_US dc.subject.lcsh Silicon--Spectra en_US dc.subject.lcsh Carbon--Spectra en_US dc.subject.lcsh Vibrational spectra en_US dc.title Vibrational spectra and structures of silicon-carbon clusters en_US dc.type Text en_US etd.degree.department Department of Physics etd.degree.level Doctoral local.college College of Science and Engineering local.department Physics and Astronomy local.academicunit Department of Physics dc.type.genre Dissertation local.subjectarea Physics and Astronomy dc.identifier.callnumber Main Stacks: AS38 .P732 (Regular Loan) dc.identifier.callnumber Special Collections: AS38 .P732 (Non-Circulating) etd.degree.name Doctor of Philosophy etd.degree.grantor Texas Christian University
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