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

Abstract

CF$_4$ 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.