Millimeter- and Submillimeter-Wavelength Spectrum and Molecular Constants ofT2O

The rotational spectrum of ${\mathrm{T}}_2$O in the ground vibrational state has been measured with high-resolution microwave techniques in the 80-640-GHz region. Forty-six previously unreported transitions have been measured and assigned. Analysis of these results and the six previously observed lines yielded the following rotation and distortion parameters (in MHz) of the Watson formulation: $\mathcal{A}=338\mathrm{}810.923\pm 0.076$, $\mathcal{B}=145\mathrm{}665.417\pm 0.044$, $\mathcal{C}=100\mathrm{}259.415\pm 0.044$, ${\Delta }_J=4.145597\mathrm{}\pm 0.0014$, ${\Delta }_{\mathrm{JK}}=-22.03898\mathrm{}\pm 0.008$, ${\Delta }_K=144.13766\mathrm{}\pm 0.006$, ${\delta }_J=1.609823\mathrm{}\pm 0.0008$, and ${\delta }_K=5.44092\mathrm{}\pm 0.01$. The usual distortion-free rotational constants derived from these are (in MHz) $A^{\prime }=338\mathrm{}808.0$, $B^{\prime }=145\mathrm{}631.9$, and $C^{\prime }=100\mathrm{}291.9$. The effective ground-state structures obtained for ${\mathrm{T}}_2$O are 0.9623 Å for the bond length and 104.6° for the bond angle. The observed inertial defect $\Delta =0.0772\mathrm{}$ amu ${\mathrm{\AA }}^2$ agrees well with the theoretically derived value of 0.0753 amu ${\mathrm{\AA }}^2$.