HIGH-RESOLUTION SPECTROSCOPY AND ANALYSIS OF THE $\nu_3/2\nu_4$ DYAD OF CF$_4$

D. R. Worton, W. T. Sturges, L. K. Gohar {\em et al.\/T. Gabard, G. Pierre and M. Takami, {\em Mol. Phys.Ch. Wenger, V. Boudon, M. Rotger, M. Sanzharov and J.-P. Champion, {\em J. Mol. Spectrosc.D. Papousek, Z. Papouskova and D. P. Chong, {\em J. Phys. Chem.\/Author Institution: Institut Carnot de Bourgogne, UMR 5209 CNRS--Universite de Bourgogne, 9 Av. A. Savary, BP 47870, F-21078 Dijon Cedex, France; Institute of Physics, St. Petersburg University, 198504 St. Petersburg, Russia; Institut fur Physikalische und Theoretische Chemie der Technischen Universitat Braunschweig, D-38106 Braunschweig, Germany; Institut de Physique de Rennes, UMR 6251 CNRS--Universit de Rennes 1, 263 Av. General Leclerc, F-35042 Rennes Cedex, France; University of Arkansas, 226 Physics Building, Fayetteville AR 72701, USACF$_4$ is a strong greenhouse gas of both anthropogenic and natural origin, {\em Environ. Sci. Technol.\/} {\bf 41}, 2184--2189 (2007).}. However, high-resolution infrared spectroscopy of this molecule has received only a limited interest up to now. The public databases only contain cross-sections for this species, but no detailed line list. We reinvestigate here the strongly absorbing $\nu_3$ region around 7.3 $\mu$m. Two new Fourier transform infrared spectra at a 0.003 cm$^{-1}$ resolution have been recorded: i) a room-temperature spectrum in a static cell with a 5 mb pressure and ii) a supersonic expansion jet spectrum at a 15 K estimated temperature. Following the work of Gabard {\em et al.\/} {\bf 85}, 735--744 (1995).\label{gab}}, we perform a simultaneous analysis of both the $\nu_3$ and $2\nu_4$ bands since a strong Coriolis interaction occurs between them, perturbing the $\nu_3$ $R$-branch rotational clusters around $J=20$. As in Ref. \ref{gab}, we also include $\nu_3-\nu_3$ microwave data in the fit. The analysis is performed thanks to the XTDS and SPVIEW programs, {\bf 251} 102--113 (2008).}. Compared to Ref. \ref{gab}, the present work extends the analysis up to higher $J$ values (56 instead of 32). Absorption intensities are estimated thanks to the dipole moment derivative value of D.~Papousek {\em et al.\/} {\bf 99}, 15387--15395 (1995).} and compare well with the experiment. The rotational energy surfaces for the $\nu_3/2\nu_4$ dyad are also examined in order to understand the distribution of rovibrational levels