The infrared spectrum of propyne in the range 6200-6700 cm-1

The absorption spectrum of propyne (CH3CCH) has been investigated in the range 6200-6700 cm (1). Data were obtained using three different experimental techniques: conventional FTIR experiments (room temperature, 0.018 cm (1) resolution, 10 m absorption path), FTIR experiments using a femtosecond broadband absorption source and a build up cavity (room temperature, 0.02 cm (1) resolution, absorption path between 1500 and 12,000 m), cavity ring down spectroscopy to probe a propyne/Ar supersonic expansion (T-rot approximate to 20 K, sub-Doppler resolution, 720 m effective absorption path length). The analysis focused on one perpendicular (nu(1) + nu(+/- 1)(6)) and four parallel (2 nu(1), nu(1) + nu(2), nu(1) + nu(3) + nu(5), nu(1) + nu(3) + 2 nu(0)(9)) bands, all perturbed by a complex system of Coriolis and anharmonic interactions. A model Hamiltonian was built, including all symmetry allowed perturbations between the upper levels of the studied bands but not accounting for additional interacting states. In total 1176 rovibrational transitions have been assigned and simultaneously fitted (sigma = 0.0029 cm (1)), leading to a set of effective rovibrational parameters. The resulting polyad structure is discussed and additional bands identified in the spectral range are tentatively assigned. (C) 2012 Elsevier B. V. All rights reserved.