Vibrationally excited states of DC5N: Millimeter-wave spectroscopy and coupled cluster calculations

The rotational spectrum of DC5N has been investigated in the millimeter-wave region for 16 vibrationally excited states which approximately lie below 760 cm−1, namely (v6v7v8v9v10v11)=(000001), (000002), (000003), (000005), (000010), (000020), (000100) (001000), (010000), (100000), (000011), (000101), (001001), (010001), (001010), and (010010). Gas-phase copyrolysis of fully deuterated pyridine and phosphorus trichloride was used to produce the semi-stable DC5N molecule. In addition to the usual l-type resonances, several vibrational interactions have been taken into account to fit properly the measured transition frequencies. The most important perturbations are caused by the cubic anharmonic interactions which mix the v6 stretching state with the 2v10 overtone and the v8+v11 and v7+v11 bending combination states. The analysis of the spectra was facilitated by theoretical predictions from CCSD(T) calculations with the cc-pVQZ basis.