Microwave Spectrum, Quadrupolar Coupling Constants, and Dipole Moment of Chlorobenzene

The microwave spectrum of chlorobenzene has been observed in the frequency range between 8000 and 30 000 Mc/sec. An analysis of this spectrum gives the following values for the rotational constants for the two isotopic species, C6H5Cl35 and C6H5Cl37; A=5672.951 Mc/sec, B=1576.774 Mc/sec, C=1233.672 Mc/sec for the Cl35 isotopic species and A=5672.530 Mc/sec, B=1532.790 Mc/sec, C=1206.571 Mc/sec for the Cl37 isotopic species. The quadrupolar coupling constants which were obtained from the quadrupolar hyperfine structure are eqQ=—71.10 Mc/sec for Cl35 and eqQ=—56.10 Mc/sec for the Cl37. The quadrupolar asymmetry parameter η cannot be determined from the microwave spectrum. The observed dipole moment is 1.78±0.06 D.