Knowledge Bank

A general applicable technique for high resolution infrared direct absorption spectroscopy of ionic complexes is presented. The setup uses the output of tunable diode lasers to sample a planar plasma based upon electron impact ionization of a gas mixture that is expanded supersonically through a long and narrow slit. A rich variety of ionic complexes and cluster ions is formed in the expansion with abundances high enough to be detectable in a production modulation scheme. The performance of the setup is demonstrated on recently obtained spectra of the $\nu 1$ fundamental of the Ar$\cdot \cdot \cdot$DN$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow><mrow\; data-mjx-texclass="ORD">+</mrow>}$ complex that coincides with the $\nu 2$+4$\nu s$ band resulting in a beautiful example of a strong Fermi interaction. \ \textbf{References}\ H. Verbraak, D. Verdes, H. Linnartz, \textit{Int. J. Mass Spectrom.} to be published (doi:10.1016/j.ijms.2007.02.042)\ H. Verbraak, M. Snels, P. Botschwina, H. Linnartz, \textit{J. Chem. Phys.} \textbf{\underline{124}}, 224315 (2006)\ H. Verbraak, J. N. P. van Stralen, J. Bouwman, J. S. de Klerk, D. Verdes, H. Linnartz, F. M. Bickelhaupt, \textit{J. Chem. Phys.} \textbf{\underline{123}}, 144350 (2005)