Knowledge Bank

From enriched $H2\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}O$ and $H2\mathrm{<mrow\; data-mjx-texclass="ORD">17</mrow>}O$ spectra recorded at the Jet Propulsion Laboratory with a grating spectrometer, reliable rotational energy levels of the (020), (100) and (001) vibrational states have been obtained. For each isotope a fit of these levels taking into account the Fermi and Coriolis type interactions has been performed leading to rotational and coupling constants very similar to those of $H2\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}O$. These fits are very satisfactory since for 85% of the levels, the difference |OBS-CALC| is less than $15\times 10-3$ $cm-1$. Moreover, a large number of line intensities have been measured with a relative precision of about 8%. They have been fitted using the method already, applied to $H2\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}O$ [J.-M. FLAUD et al., J. Mol. Specros. 55, 278 (1975)]. A comparison is given between the results obtained for the three isotopes.