Magnetic Properties and Molecular Quadrupole Tensor of the Water Molecule by Beam-Maser Zeeman Spectroscopy

The hyperfine and Zeeman components of the 3_–2–2₂ and 4₃–5₁ transitions of D₂O, the 2₂−2₁ transition of HDO, and the 6₋₅−5₋₁ transition of H₂O have been measured with a beam‐maser Zeeman spectrometer. This allowed determination of the elements of the magnetic moment tensor $G_{\mathrm{gg}}$ and of the anisotropic part of the magnetic susceptibility tensor ${\mathrm{(\chi }}_{\mathrm{gg}}{\mathrm{–\chi }}_{\mathrm{Av}})$ for D₂O. The best fit results are (for ${\chi }_{\mathrm{gg}}{\mathrm{–\chi }}_{\mathrm{Av}}$ in 10⁻⁸kHZ G⁻²): $G_{\mathrm{aa}}{\text{\hspace{0.17em}=\hspace{0.17em}0.32530(10), G}}_{\mathrm{bb}}{\text{\hspace{0.17em}=\hspace{0.17em}0.36009(22), G}}_{\mathrm{cc}}{\text{\hspace{0.17em}=\hspace{0.17em}0.32513(15), χ}}_{\mathrm{aa}}{\mathrm{–\chi }}_{\mathrm{Av}}{\text{\hspace{0.17em}=\hspace{0.17em}3.88(20), χ}}_{\mathrm{bb}}{\mathrm{–\chi }}_{\mathrm{Av}}{\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}1.66(40), χ}}_{\mathrm{cc}}{\mathrm{–\chi }}_{\mathrm{Av}}\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}2.23(30)}$ . From these values the elements of the molecular quadrupole moment tensor for D₂O have been determined (in 10⁻²⁶ esu·cm): ${\theta }_{\mathrm{aa}}{\text{\hspace{0.17em}=\hspace{0.17em}2.72(2), θ}}_{\mathrm{bb}}{\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}0.32(3), θ}}_{\mathrm{cc}}\text{\hspace{0.17em}=\hspace{0.17em}−2.40(2)}$ . The sign of the molecular electric dipole moment and the validity of the isotopic invariance of the electronic charge distribution have been investigated by comparing the molecular magnetic moments of D₂O, HDO, and H₂O. The obtained experimental values for several one‐electron properties are in fair agreement with recent accurate ab initio calculations.