Rotational spectrum of the v12=1, v13=1 and v7=1 vibrational states of CH3CCCCH

We have used the theoretical predictions from anharmonic force field calculations reported in our previous work [J. Mol. Spectrosc. 253 (2009) 106] to assign the pure rotational spectra in the v12 and v13 doubly degenerate bending modes of the main isotopic species of methyldiacetylene. The key experimentally determined spectroscopic constants are found to be in good agreement with calculation. The rotational spectrum in the lowest singly degenerate mode, the v7 stretching mode, has also been assigned. The corresponding rotational constants require a revision of the previously reported computational results and point to the possibility of an interaction between v7 and 2v13.