Submillimetre-wave spectrum of diacetylene and diacetylene-d2

High-resolution infrared spectroscopy of diacetylene below 1000 cm−1

“…In the present work, we have investigated the ro-vibrational bands ν 8 , ν 7 + ν 9 , ν 8 + ν 9 − ν 9 , ν 7 + 2ν 9 − ν 9 , and ν 3 − ν 9 . The IR data have been analysed together with the previous mm-wave measurements of the ν 8 − ν 6 and ν 8 + ν 9 − (ν 6 + ν 9 ) bands [16], so that our analyses deal with a manifold of states involving excitation of the v 3 stretch (Σ + g ) and all the four bending quanta (…”

“…For instance, the intensity of the ν 8 − ν 6 band is substantially enhanced and, since its origin is located below 100 GHz, it provides a mean of detecting diacetylene through millimetre-wave (mm-wave) spectroscopy [14,15]. Very recently, we have extended to the submillimetre-wave (submm-wave) region the study of this band and of its ν 8 +ν 9 −(ν 6 +ν 9 ) hot band, performing a complete analysis of the l-type resonance effects and of the above mentioned anharmonic interaction affecting the v 8 = v 9 = 1 state [16]. However, no direct information on the v 3 = 1 state could be obtained from mm-wave spectra, thus the spectroscopic constants of this level had to be estimated from recent theoretical calculations [17,18].…”

“…The model adopted for the analysis includes the rotational and vibrational l-type resonances active between the various l-sublevels of the multiple bending excited states, and also considers the two anharmonic interactions which couple v 3 = 1 with the v 8 = v 9 = 1 combination and the v 7 = 2 overtone states through the normal coordinates cubic potential constants φ 389 and φ 377 . The previously recorded mmwave transition frequencies [16] were also taken into account in order to obtain the best set of spectroscopic parameters for the ground state and for the v 6 = 1 and v 8 = 1 bending states.…”

Accurate ro-vibrational rest frequencies of DC4H at infrared and millimetre wavelengths

“…by reaction of 1, 4-dichloro-2-butyne (Aldrich) with sodium hydroxide dissolved in a nearly equimolar mixture of H 2 O and D 2 O. The rotational spectra of DC 4 H in the ground state and in the excited bending states have been recorded in selected frequency regions between 85 and 615 GHz, using the mm-wave spectrometer employed to record the v 8 − v 6 difference band for the symmetric isotopologues HC 4 H and DC 4 D (Bizzocchi et al 2010). Briefly, the radiation sources were phase-locked Gunn oscillators (75−115 GHz range) equipped with various frequency multipliers, and the absorption cell was a 3 m long glass tube sealed by PTFE windows.…”

“…In this paper we present the results of a comprehensive new laboratory investigation of the ro-vibrational spectrum of DC 4 H. Following what we have done in our previous papers on HC 4 H (Bizzocchi et al 2010(Bizzocchi et al , 2011, our main effort aims to provide state-of-the-art spectroscopic data on DC 4 H to the astronomical community. These data are very useful for infrared and/or millimetre studies.…”