Millimeter- and submillimeter-wavelength spectra and molecular constants of HTO and DTO

The rotational spectrum of DTO and HTO in the ground vibrational state has been measured with high-resolution microwave techniques in the 50-700-GHz region. We have measured and assigned 41 transitions of DTO. Analysis of these data yielded the following rotation and distortion parameters of the Watson formulation (in MHz): $\mathcal{A}=410\mathrm{}174.145\pm 0.078$, $\mathcal{B}=172\mathrm{}101.952\pm 0.045$, $\mathcal{C}=199\mathrm{}127.850\pm 0.045$, ${\Delta }_J=5.199034\mathrm{}\pm 0.003$, ${\Delta }_{J\mathrm{K}}=-15.50411\mathrm{}\pm 0.015$, ${\Delta }_K=180.31052\mathrm{}\pm 0.010$, ${\delta }_J=1.941256\mathrm{}\pm 0.0010$, ${\delta }_K=12.8893\mathrm{}\pm 0.012$. We measured 22 previously undetected transitions of HTO. Analysis of these, together with 26 lines already known, gave the following rotation and distortion parameters (in MHz): $\mathcal{A}=677\mathrm{}849.040\pm 0.170$, $\mathcal{B}=198\mathrm{}197.489\pm 0.128$, $\mathcal{C}=150\mathrm{}462.412\pm 0.128$, ${\Delta }_J=5.212023\mathrm{}\pm 0.003$, ${\Delta }_{\mathrm{JK}}=48.52276\mathrm{}\pm 0.02$, ${\Delta }_K=271.27533\mathrm{}\pm 0.06$, ${\delta }_J=1.414126\mathrm{}\pm 0.0005$, ${\delta }_K=51.32833\mathrm{}\pm 0.07$. The usual distortion-free rotational constants derived from these Watson constants are (in MHz): for DTO, $A^{\prime }=410\mathrm{}160.3$, $B^{\prime }=172\mathrm{}050.2$, $C^{\prime }=119\mathrm{} 183.6$; and for HTO, $A^{\prime }=677\mathrm{} 777.7$, $B^{\prime }=198\mathrm{} 089.7$, $C^{\prime }=150\mathrm{} 604.4$. The latter constants and corresponding ones previously obtained for other isotopic species of water were used to calculate substitutional structures of the molecule. The averages of the structural parameters thus obtained are 0.9577 Å for the bond length and 104.66° for the bond angle.