The FANTASIO+ set-up to investigate jet-cooled molecules: Focus on overtone bands of the acetylene dimer.

Keevin Didriche (1) , Clement Lauzin (1) , Tomas Foldes (1) , Xavier de Ghellinck d'Elseghem Vaernewijck (1) , Michel Herman (1)

1 Service de Chimie Quantique et Photophysique

The experimental set-up FANTASIO, for "Fourier trANsform, Tunable diode and quadrupole mAss spectrometers interfaced to a Supersonic expansIOn" (M. Herman, K. Didriche, D. Hurtmans, B. Kizil, P. Macko, A. Rizopoulos, and P. Van Poucke, Mol. Phys. 105, 815 (2007)) built in Brussels has been updated. The turbomolecular pumping system of the supersonic expansion has been doubled and new mirrors, with reflectivity 99.999% instead of 99.99%, have been set in the CW-cavity ring down spectrometer (CW-CRDS) probing jet-cooled molecules. The changes all together result in a signal to noise increased by up to a factor 10, around 1.5 microns. These improvements are demonstrated with various acetylene data in the 2CH excitation range, including the assignment of a new sub-band of acetylene-Ar, with K'-K" = 2-3. The focus is set on the acetylene dimer. Overtone sub-bands, with b- and a-type structures, are identified for the first time in the literature. The former are assigned to vibrational excitation in the hat unit of the T-shaped dimer, the latter, tentatively, to vibrational excitation in both units. The relevance of the overtone data on acetylene dimers for space remote sensing is highlighted.

Mots clés: Physical Sciences

Keevin Didriche, Clement Lauzin, Tomas Foldes, Xavier de Ghellinck d'Elseghem Vaernewijck, Michel Herman. The FANTASIO+ set-up to investigate jet-cooled molecules: Focus on overtone bands of the acetylene dimer.. Molecular Physics, 2010, pp.1. ⟨10.1080/00268976.2010.489525⟩. ⟨hal-00598574⟩