The Cologne Carbon Cluster Experiment: ro-vibrational spectroscopy on C 8 and other small carbon clusters

Abstract

We report on our ongoing efforts in obtaining the IR-spectra of the linear carbon cluster molecules C n with n=8–13. So far C 8, C 9, C 10, and C 13 have been recorded at Cologne. With the exception of C 8 all assignments have been secured. For C 8 a tentative assignment could be derived with the bandcenter of the σ u antisymmetric stretching mode located at ν 0=2067.9779 cm −1 and a preliminary rotational constant in the vibrational ground state of B″=0.02068 cm −1. The measured signal to noise ratio of the ro-vibrational band is fairly weak and thus the lower J ro-vibrational transitions can not be assigned with certainty. As a consequence the band center remains uncertain by 4 J or 0.17 cm −1. For a more reliable assignment the sensitivity of the system has to be increased by at least one order of magnitude. The envisaged sensitivity increase of our experiment will be discussed along with the intention to perform terahertz observations of the low energetic bending ro-vibrational spectra. These sub-mm wave measurements will be carried out simultaneously with the IR measurements.