Molecular beam Zeeman effect and dipole moment sign of ClF

Molecular beam electric resonance spectroscopy has been used to observe hyperfine, Stark, and Zeeman properties of chlorine monofluoride. The dipole moment from Zeeman data is 0.85(15), −FCl+, in agreement with the known magnitude. The sign obtained here is the opposite of earlier, less precise, Zeeman results but agrees with calculations and van der Waals molecule experiments. Hyperfine, Stark, and Zeeman properties for 35ClF and 37ClF are reported, including polarizability anisotropy, α∥−α⊥=1.32(8) Å3, molecular quadrupole moment, ϑ∥=1.54(7) ×10−26 esu⋅cm2, and the chlorine quadrupole coupling constant derivative, deQq/dR=−90(20) MHz/Å.