HIGH RESOLUTION INFRARED STUDY OF THE $v_{5}$ AND $v_{6}$ PERPENDICULAR BANDS OF $FC\ell^{18}O_{3}$

Abstract

The IR spectra of isotopiclly pure samples of the two molecules $F^{35}C\ell^{18}O_{3}$ and $F^{37}C\ell^{18}O_{3}$ have been recorded with a Bruker 120 HR Fourier transform spectrometer at a resolution of ${\sim} 0.003 cm^{-1}$. The two perpendicular fundamentals $v_{5}$ and $v_{6}$ localed at $565.10234 (4)$ and $390.54017 (3) cm^{-1}$ for $F^{35}C\ell^{18}O_{3}$ and 562.24615 (5) and $390.49788 (3) cm^{-1}$ for $F^{37}C\ell^{18}O_{3}$ have been analyzed in detail, Ground statc consunts, up to the H's, have been fixed to values obtained in a previous $work^{1}$. J and K values up to 98 and 84 respectively have been reached. The spectrum of $v_{5}$ is dominated by a $\Delta K = \pm 3$ resonance affecting almost all levels. This yields accurate values of the $A_{o}$ and $D^{0}_{K}$ molecular constants. We shall report for these four bands a set of upper state spectroscopic constants, which allows us to reproduce the experimental data with a standard deviation of $0.0003 cm^{-1}$ on residuals.