The high-resolution infrared spectrum of DC4H from 450 to 1100 cm−1: overtone, combination and hot bands.

The high-resolution infrared spectrum of monodeuterated diacetylene has been recorded in the 450– 1100 cm−1 spectral region by Fourier transform infrared spectroscopy. Seven new bands have been identified: the ν3 fundamental (C–C stretch), and the ν8 + ν9, ν7 + ν8, 2ν7, 2ν8, ν8 + ν9 − ν9, and ν6 + ν9 − ν9 combination, overtone, and hot bands. The assigned transitions, together with those previously reported for the fundamental bands [F. Tamassia, L. Bizzocchi, C. Degli Esposti, L. Dore, M. Di Lauro, L. Fusina, M. Villa, and E. Canè, Astron. Astrophys. 549, A38 (2013)], form a comprehensive data set which comprises more than 2500 ro-vibrational transitions, and involves all singly and most doubly excited vibrational states of DC4H lying below 1000 cm−1. Rotational and vibrational l-type resonance effects among the sub-levels of excited bending states were considered in the analysis, which also included a careful treatment of the various anharmonic interactions coupling many vibrational states lying above 600 cm−1. Reliable and unambiguous spectroscopic parameters were obtained for each investigated state, including the rotational and centrifugal distortion constants Bv and Dv, the l-type doubling parameter qt, the anharmonicity constants xL(89), xL(69), and the vibrational l-type terms r89, r69 for the v8 = v9 = 1 and v6 = v9 = 1 bend-bend combination states.