Portion of the J = 33 ← 32 transition of the rotational spectrum of C₂H₅C≡C–C≡N taken at a Stark field of about 150 V/cm. The values above several of the absorption peaks refer to the K_-1 pseudo-quantum number. It was not possible to definitely assign values of K_-1 higher than 15 because of overlapping transitions (extreme right of the picture). The most intense line to the extreme left consists of the unresolved K_-1 = 5 and 6 transitions.