Dipole moment of water from Stark measurements of H2O, HDO, and D2O

The equilibrium dipole moment of the water molecule has been determined from Stark effect measurements on two H2O, one D2O, and six HDO rotational transitions. The variation of the dipole moment projection operator with rotational state is taken into account and expressions are given for this operator evaluated in the ground vibrational states of the three isotopes. The value obtained for the equilibrium dipole moment is |0μx| = 1.8473 ± 0.0010 D. The effective dipole moments in the principal axis energy representation are |μb (HOH)| = 1.8546 ± 0.0006 D, |μb (DOD)| = 1.8558 ± 0.0021 D and |μb (DOH)| = 1.7318 ± 0.0009 D, |μa (DOH)| = 0.6567 ± 0.0004 D.