Millimeter and Submillimeter Wave Spectrum ofO218

Abstract

Fine-structure transitions in the millimeter wavelength region and the $n(J)=1(2)\ensuremath{\rightarrow}3(2)$ submillimeter wavelength rotational transition have been measured with high precision. The submillimeter radiation was generated by a harmonic multiplier and detected by a silicon bolometer operated at 1.5 \ifmmode^\circ\else\textdegree\fi{}K. The measured 1(2) \ensuremath{\rightarrow} 3(2) frequency of $^{18}\mathrm{O}_{2}$ is 378 831.51(20) MHz. A remeasurement of the 1(2) \ensuremath{\rightarrow} 3(2) frequency for $^{16}\mathrm{O}_{2}$ yielded the value 424 763.12(10) MHz. Analysis of the results yielded the following values of the molecular constants for $^{18}\mathrm{O}_{2}$: ${B}_{0}=38313.721(2)$ MHz, ${\ensuremath{\lambda}}_{0}=59496.708(12)$ MHz, ${\ensuremath{\lambda}}_{1}=0.0521(3)$ MHz, ${\ensuremath{\mu}}_{0}=\ensuremath{-}224.438(3)$, ${\ensuremath{\mu}}_{1}=\ensuremath{-}0.00029(5)$ MHz, ${B}_{e}=38518.6(6.3)$ MHz, and ${r}_{e}=1.20743(10)$ \AA{}. The values agree well with those predicted from isotopic corrections of the $^{16}\mathrm{O}_{2}$ values. The equilibrium constants were obtained with the aid of vibration-rotation interaction constants from optical spectroscopy.