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MASS-SELECTIVE MATRIX-ISOLATION SPECTROSCOPY: FT-IR SPECTRA OF CYANOACETYLENE AND TETRACYANOETHYLENE IONS AND THEIR IONIC FRAGMENTS

Please use this identifier to cite or link to this item: http://hdl.handle.net/1811/20617

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Title: MASS-SELECTIVE MATRIX-ISOLATION SPECTROSCOPY: FT-IR SPECTRA OF CYANOACETYLENE AND TETRACYANOETHYLENE IONS AND THEIR IONIC FRAGMENTS
Creators: Smith-Gicklhorn, A. M.; Frankowski, Marcin; Lorenz, M.; Bondybey, V. E.; Kolos, R.
Issue Date: 2002
Abstract: Recent spectroscopic results from a new setup for the deposition of mass-selected ions in neon matrices are presented. Gaseous precursor substances are ionized in a homebuilt electron impact source, the ions extracted and deflected by $90^{\circ}$ into a quadrupole mass filter with unity mass resolution up to 500 amu. The mass-selected cations are deposited simultaneously with an excess of electrons, to maintain overall sample neutrality and prevent buildup of space charges, and neon gas onto a reflective substrate held at 7 K. Fourier-transform infrared spectra from such samples using cyanoacetylene and tetracyanoethylene reveal new infrared transitions for several cations. The strong infrared signal observed for the asymmetric stretch of $CNC^{+}$ and the appearance of the corresponding band for $^{13}CNC^{+}$ in its natural isotopic abundance, demonstrates the sensitivity and usefulness of the apparatus. A combination band of $CNC^{+}$ is also observed, revealing its low-frequency bend. Using this setup, the infrared spectra of cyanoacetylene $ions^{a}$ $(H(D)C_{3}N^{+}$ and $C_{3}N^{+}_{2}$) and tetracyanoethylene ions and ionic $fragments^{b}$ $(C_{6}N^{+}_{4}$, $C_{6}N^{-}_{4}$, $C_{6}N^{+}_{3}$, $C_{5}N^{+}_{3}$, and $C_{3}N^{+}_{2}$) are observed for the first time. The assignment of the numberous observed vibrations of these ions are well-supported by our density-functional calculations. Using this apparatus and the sensitive LIF techique, the assignment of a rich emission spectrum with origin near 440 nm is confirmed to be due to mass 88 or $C_{5}N_{2}$ $neutral^{c}$ as subsequently verified by a cavity ringdown measurement of Linnartz, Maier et al.
URI: http://hdl.handle.net/1811/20617
Other Identifiers: 2002-TG-09
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