Microwave spectrum and molecular constants ofO16O18

Measurements of millimeter-wave fine-structure transitions and the $n\left(J\right)=0\mathrm{}\left(1\right)\mathrm{}\to 2\left(1\right)\mathrm{}$ rotational transition of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ have been made with high precision. From analysis of the results the following molecular constants of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ were obtained: $B_0=40\mathrm{}707.408\left(10\right)\mathrm{}$ MHz, $B_1=-0.129\mathrm{}$ MHz, ${\lambda }_0=59\mathrm{}499.097\left(43\right)\mathrm{}$ MHz, ${\lambda }_1=0.053\mathrm{}12\left(80\right)\mathrm{}$ MHz, ${\mu }_0=-238.488\mathrm{}\left(7\right)\mathrm{}$ MHz, ${\mu }_1=-0.000\mathrm{}619\left(116\right)\mathrm{}$ MHz, $B_e=40\mathrm{}931.7\left(6.9\right)\mathrm{}$ MHz, $r_0=1.210\mathrm{}751\left(16\right)\mathrm{}$ Å, and $r_e=1.207\mathrm{}429\left(103\right)\mathrm{}$ Å. The equilibrium values were obtained with the aid of vibration-rotation interaction constants from optical spectroscopy.