THE INFRARED ABSORPTION SPECTRUM OF $C_{2}H_{2}$ AROUND $1300 CM^{-1}$

(1) K.F. Palmer, M.E. Mickelson and K.N. Rao, J. Mol. Spectrosc. 44, 131-44 (1972). (2) J. Pliva, J. Mol. Spectrosc. 44. 145-64 (1972), 44, 165-82 (1972). (3) J.K.G. Watson, M. Herman, J.C. Van Craen and R. Colin, J. Mol. Spectrosc. 95, 101-132 (1982).Author Institution: Laboratoire de Chimic Physique Moleculaire, C.P. 160, Universit\'{e} Libre de BruxellesThe absorption spectrum of $C_{2}H_{2}$ has been recorded with a resolution of $\sim 0.003 cm^{-1}$ using a Bruker IFS.120HR Fourier Transform Spectrometer, between 1200 and $1450 cm^{-1}$. The spectrum, which was previously studied in the literature (1) at lower resolution, is reinvestigated. Several new bands will be reported. A full Hamiltonian dealing with vibrational and rotational $\ell$-doubling interactions, inspired from (2,3), is used to improve the previous rovibrational constants concerning the $\nu_{4}$ and $\nu_{5}$ bending modes. The use of a unique model to deal simultaneously with all observed transitions will allow to consider relative intensities features between the various $\Delta \ell$ subbands. It is hoped that this approach will help reconsidering the absolute intensities problem in an atmospheric context. This work is part of the belgian contribution to EUROTRAC, sponsored by the SPPS (Belgium)