S. ROBERT, M. HERMAN, Service de Chimie quantique et Photophysique, CP160/09, Université Libre de Bruxelles (U.L.B.), Ave. F.-D. Roosevelt, 50, B-1050, Bruxelles, Belgium; A. FAYT, Laboratoire de Spectroscopie Moléculaire, Université Catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-La-Neuve, Belgium; G. DI LONARDO, L. FUSINA AND F. TAMASSIA, Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento, 4, I-40136, Bologna, Italy.

All known vibration-rotation absorption lines of 12CH13CH accessing levels up to 6750 cm-1 were gathered from the lite\-rature. They were fitted simultaneously to J-dependent Hamiltonian matrices exploiting the well known vibrational polyad or cluster block-diagonalization, in terms of the pseudo quantum numbers Ns = v1+v2+v3 and Nr = 5v1+3v2+5v3+v4+v5, and accounting also for l-parity and e/f symmetry properties. The anharmonic interaction coupling terms known to occur from a pure vibrational fit in this acetylene isotopologue were included in the model. The results will be presented and discussed.