THE DIPOLE-MOMENT OF WATER .2. ANALYSIS OF THE VIBRATIONAL DEPENDENCE OF THE DIPOLE-MOMENT IN TERMS OF A DIPOLE-MOMENT FUNCTION

The electric dipole moment measurements on H2O, presented in the previous paper, are analyzed here. First, centrifugal distortion effects were removed from the observed moments. The rotationless moments were then considered in terms of a dipole moment function for water. The moments were combined with first dipole derivatives to determine second derivatives of the moment with respect to normal coordinates. This procedure indicated inconsistencies between existing first derivatives and the permanent moments, which were attributed to approximations made when the first derivatives were obtained from the infrared intensity data. A combined analysis of the original transition moment data and the permanent moments yielded consistent first and second derivatives, but with less accuracy than the input data. The overall results include: the first accurate determination of the equilibrium value, and vibrational energy dependence, of the dipole moment; new second derivative values; and an increased awareness of the need for more complete analysis of the vibrational properties of water.