Millimetre and infrared spectrum of DC_4_H

In contrast, monodeuterated diacetylene (DC_4_H) has not been detected in space so far owing to the low isotopic abundance of deuterated species but also to the rather poor laboratory spectroscopic characterisation of this molecule. The aim of this work is to provide accurate spectroscopic parameters for DC_4_H to achieve reliable predictions for both its spectra at millimetre and infrared wavelengths.

We studied the rotational spectrum of DC_4_H in the range 85-615GHz by millimetre-wave spectroscopy and the infrared spectrum below 1000cm-1 by high-resolution, Fourier-transform spectroscopy. Several pure rotational transitions were recorded in the ground state and in excited vibrational bending states. The three fundamental bands v6, v7, and v8 have been identified and assigned in the infrared spectrum.