The absorption spectrum of 12C2H2 between 12800 and 18500cm−1 II. Rotational analysis

The rotational structure of the vibrational bands of 12C2H2 is investigated in three spectral energy regions not previously systematically explored at high resolution, 12800–13500 cm−1, 14000–15200 cm−1 and 16500–18360 cm−1, on the basis of new spectral data recorded by intracavity laser absorption spectroscopy. The rotational analysis of 17 new absorption bands arising from the ground state is reported (11 Σu + − Σg + bands and 6Πu − Σg + bands). Four bands in the range studied show strong perturbations affecting both the line positions and intensities. Their detailed analysis is performed in order to determine the nature of the coupling schemes, the vibrational species and the rotational constants of the perturber states. Altogether, the vibration-rotation parameters of 21 newly observed vibrational states are derived.