Infrared spectroscopy C6D6−Rgn(n=1,2)

Benzene-noble gas complexes were one of the earliest topics of interest in spectroscopic investigation of van der Waals (vdW) complexes. Smalley et al.\footnote{S. M. Beck, M. G. Liverman, D. L. Monts and R. E. Smalley, J. Chem. Phys. \textbf{70}, 232 (1979).} observed \chem{C_6H_6–(He)}$_{1,2}$ vdW complexes in the late 1970s by means of electronic spectroscopy. A recent study on the same species was done by M. Hayashi et al.\footnote{M. Hayashi, Y. Ohshima , Chem. Phys. \textbf{419}, 131 (2013).}at higher resolution (250 MHz). Here, we present the infrared observation of \chem{C_6D_6-Rg_n} (n=1,2) with the rare gas being He, Ne, or Ar, in the regions of \nub{12} fundamental band of \chem{C_6D_6} ($\mathtt{\sim}$2289 \wn) and the \nub{2} + \nub{13} combination band ($\mathtt{\sim}$2275 \wn) which are coupled by a Fermi resonance. The spectra were observed at a resolution of ~60 MHz using a tunable optical parametric oscillator to probe a pulsed supersonic-jet expansion from a slit nozzle. In the case of \chem{C_6D_6-Rg} dimers, the spectra were assigned to a symmetric top with \textit{C}$_{6v}$ symmetry with the rare gas atom being located on the \textit{C}$_{6}$ symmetry axis. To observe \chem{C_6D_6-Rg_2} trimers, the nozzle was cooled using a closed-cycle methanol refrigerator and the spectra were simulated with a rotational temperature of 1.3K. The spectra of the \chem{C_6D_6-Rg_2} trimers were in agreement with a \textit{D}$_{6h}$ symmetry structure, where the rare gas atoms are positioned above and below the \chem{C_6D_6} plane. Data analysis and observation are presently ongoing