Knowledge Bank

$TaO,TaO2,WO$ and $WO2$, prepared either by vaporization of the oxide and/or by passing $O2\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}$ or $O2\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}$ over the hot metal, were trapped in neon or argon matrices at $4\circ K$ or $20\circ K$. Their absorption spectra were measured between 3000 and 9000 {\AA} and between $3\mu$ and $35\mu$. The kind of information obtained is exemplified by the case of TaO. Here transitions to at least seven excited electronic states could be distinguished by the effect of isotopic substitution upon the spectrum. The vibration frequency in most of these states could be determined and was found to vary between 886 and $941cm-1$ for $TaO16$ in neon. Three of the $(0,0)$ transitions, at 3737, 4141, and 4273 {\AA} in neon, have been observed in the gas of 3747, 4155, and 4282 {\AA} and analyzed by Premaswarup and $Barrow.1$ The matrix observations indicate that their $a\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta$ state is the ground state of TaO and that the molecule is trapped in neon in both the $a\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta 5/2$ and $a\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta 3/2$ multiplet levels, where $A\approx -850cm-1$. The spectra of trapped WO (ground state = $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +)$ can be analyzed in an analogous way, but the gas data are less complete. The linear triatomic molecules exhibit an electronic transition in which they are bent in the upper state. Ligand-field $theory2$ has been used for the interpretation and correlation of the matrix spectra.