Rovibrational laser jet-cooled spectroscopy of SF$_6$-rare gas complexes in the v$_3$ region of SF$_6$

P. Asselin (1) , A.C. Turner (2) , Laurent Bruel (3) , V. Brenner (4) , M.-A. Gaveau (4) , M. Mons (4)

1 MONARIS - De la Molécule aux Nanos-objets : Réactivité, Interactions et Spectroscopies
2 EPS - Department of Earth and Planetary Science [UC Berkeley]
3 DPME - Département de recherche sur les Procédés et Matériaux pour les Environnements complexes
4 LIDYL - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)

High resolution infrared spectroscopy combining an external cavity quantum cascade laser with a pulsed pin hole supersonic jet is used to investigate small van der Waals (vdW) hetero clusters containing SF$_6$ and rare gas (Rg) atoms in the v$_3$ region of SF$_6$. In a first step, the rovibrational band contours of parallel and perpendicular transitions of 1:1 SF$_6$-Rg hetero dimers are simulated to derive ground and excited state parameters and hence S-Rg distances with a precision better than 0.5 $\mathring{A}$. Due to the strong overlap of the SF$_6$-Ne spectrum by the intense SF$_6$ monomer one, the S-Ne distance could be only estimated from combining rules, which turned out to be very predictive for the other experimental S-Rg distances (deviation < $\pm$ 0.5 percent). In a second step, the signature of larger hetero clusters containing up to three Rg atoms is identified on the grounds of reduced red shifts of 1:2 and 1:3 complexes, normalized to the average red shift measured for the 1:1 complex. For the 1:1 and 1:2 complexes, reduced red shifts are shown to be nearly independent upon the Rg atom which suggests comparable structures in agreement with the C3v symmetry and confirms our assignments. Beyond the 12 complexes, the assignment of the two more red shifted remaining bands to 1:3 SF$_6$-Ar and SF6Kr hetero tetramers validates the red shift additivity rule up to three Rg atoms in the case of SF$_6$. Lastly, we evidence that the band shifts of the 1:1 SF$_6$-Rg hetero dimers can be correctly reproduced using a one-dimensional model for the intermolecular interaction based on the Buckingham potential which contains both longrange attractive and short-range contributions and enables to estimate the well depths of these vdW heterodimers

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

P. Asselin, A.C. Turner, Laurent Bruel, V. Brenner, M.-A. Gaveau, et al.. Rovibrational laser jet-cooled spectroscopy of SF$_6$-rare gas complexes in the v$_3$ region of SF$_6$. Physical Chemistry Chemical Physics, 2018, 20, pp.28105-28113. ⟨10.1039/C8CP04387F⟩. ⟨cea-02339625⟩