: |
: |
|---|
A. M. SMITH-GICKLHORN, M. FRANKOWSKI, M. LORENZ, V. E. BONDYBEY, Institut für Physikalische und Theoretische Chemie, Lichtenbergstraße 4, D-85747 Garching, Germany; AND R. KO\LOS, Institute of Physical Chemistry of the Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw, Poland.
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 90o 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 13CNC+ 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\footnoteA.M. Smith-Gicklhorn, M. Lorenz, R. Ko\los and V.E. Bondybey J.~Chem.~Phys. \underline\textbf115, 7534-7542 (2001). (H(D)C3N+ and C3N2+) and tetracyanoethylene ions and ionic fragments (C6N4+, C6N4-, C6N3+, C5N3+, and C3N2+) 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 C5N2 neutral \footnoteA.M. Smith-Gicklhorn, M. Lorenz, M. Frankowski, R. Ko\los and V.E. Bondybey Chem. Phys. Lett. \underline\textbf351, 85-91 (2002). as subsequently verified by a cavity ringdown measurement of Linnartz, Maier et al.