A priori predictions of the rotational constants for HC₁₃N, HC₁₅N, and C₅O

Ab initio molecular orbital theory is used to estimate the rotational constant for several carbon-chain molecules that are candidates for discovery in interstellar space. These estimated rotational constants can be used in laboratory or astronomical searches for the molecules. The rotational constant for HC13N is estimated to be 0.1073±0.0002 GHz and its dipole moment 5.4 D. The rotational constant for HC15N is estimated to be 0.0724 GHz,with a somewhat larger uncertainty. The rotational constant of C5O is estimated to be 1.360±2% GHz and its dipole moment 4.4. D. © 1989.