Rotational spectra of DCCCN in some excited vibrational states

We have observed and analyzed the millimeter-wave spectrum of deuterated cyanoacetylene (DCCCN) in 12 excited vibrational states. The Hamiltonian of K. M. T. Yamada, F. W. Birss, and M. R. Aliev (J. Mol. Spectrosc. 112, 347–356 (1985)) has allowed the determination of accurate rotational and l-type doubling constants for the following isolated states: (v₄, v₅, v₆, v₇) = (1001), (0001), (0002), (0003), (0010), (0100), (0101), (0011), and 0012). The anharmonic resonance between the (1000), (0020), and (0004) states has been observed and analyzed, yielding the unperturbed rotational constants and the Fermi interaction constant.