Knowledge Bank

Microwave spectroscopic $measurements1$ of the Zeeman effect in chlorine monofluoride, ClF, produced a dipole moment sign of -ClF+. Ab initio $calculations2$ and the observation of the dipole moment and structure of the hydrogen fluoride-chlorine fluoride van der Waals’ $complex3$ both produced a sign for +ClF- in agreement with chemical intuition. To resolve this situation, the Zeeman effect of C1F has been reinvestigated using the high resolution of molecular beam electric resonance spectroscopy. This study gives $\mu =0.85(15)D+C1F$- in good agreement with the known magnitude of 0.888D. This result indicates the earlier Zeeman study was in error. In view of this result, it seems prudent to consider dipole moment signs undetermined if either the Zeeman effect dipole moment has quoted error limits approaching 100% or if the Zeeman moment magnitude differs from the known magnitude by 100%.