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Matrix isolation FTIR spectroscopic and DFT studies of metal-carbide clusters
Bejjani, Micheline
Bejjani, Micheline
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[Fort Worth, Tex.] : Texas Christian University,
Date
2011
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Abstract
Several metal containing molecules, including MgCN, NaCN, KCl, AlOH, and AlF have been observed in the interstellar medium. Additionally, transition metals have been observed. Many carbon containing molecules have also been observed in astrophysical sources. The purpose of the present research is to provide information on the spectral properties of metal carbide molecules that are potentially observable in space. Additional interest for studying small metal carbide molecules is the understanding of larger clusters including metallofullerenes and metallocarbohedrenes, and the catalytic growth of carbon nanotubes. FTIR spectra were obtained by condensing the vapor produced by dual laser ablation of metal and carbon rods in an argon matrix at ~12K. Comparison of the observed 13C enriched vibrational spectra to the DFT simulated isotopic spectra has enabled the identification of vibrational fundamentals of linear MnC3, linear MgC3-, and chain ZnC3.^The linear MnC3 has been detected for the first time. Its ?1(s) vibrational fundamental has been observed at 1846.9 cm-1. Although previous photoelectron studies by Wang and Li have reported evidence for the cyclic isomer of MnC3, their assignment was inconclusive since the linear and fanlike structures have been found to lie very close in energy, and the observed PE frequency matched the frequencies predicted for the vibrational fundamentals of both the linear and the fanlike isomers of MnC3. Theoretical investigations of MgC3- have indicated that the bent, linear, fan and kite structures are close in energy, and thus are potentially observables. In the present work, the ?1(s) asymmetric carbon stretching mode of linear MgC3- has been observed at 1797.5 cm-1. A second absorption at 1190.1 cm-1 which is correlated in intensity to the ?1(s) has tentatively been assigned to the ?2(s) vibrational fundamental.^Although DFT calculations on ZnC3 have indicated that the linear, bent and kite structures are very close in energy, in the present research one vibrational fundamental of bent ZnC3 in its 1A' state was observed at 1858.9 cm-1.
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Subject(s)
Fourier transform infrared spectroscopy.
Transition metal carbides.
Density functionals.
Transition metal carbides.
Density functionals.
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Dissertation
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Physics and Astronomy