Knowledge Bank

The near infrared $(4000-14000cm-1)$ spectrum of FeO has been recorded with the 1-meter FT spectrometer at Kitt Peak National Observatory. Like that of the orange system of FeO, the spectrum is very complex and highly perturbed. It consists of two systems: $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Phi -X5\Delta$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Pi -X5\Delta$. All three states exhibit good case (a) behaviour and have electronic configurations (in single configuration approximation): $X\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Delta i3d\delta 33d\pi 24s\sigma 1$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Phi i,\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Pi i3d\delta 33d\pi 23d\sigma 14s\sigma 1(02p\pi )3$. The $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Phi$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Pi$ states lie only about $250cm-1$ apart and therefore overlap each other extensively. These states are perturbed by at least three different electronic states, one of which is a $\Sigma$ state. The most likely candidates for the other perturbing states are $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi ,\mathrm{<mrow\; data-mjx-texclass="ORD">7</mrow>}\Pi ,\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Phi$, and $\mathrm{<mrow\; data-mjx-texclass="ORD">7</mrow>}\Phi$, all derived form the same electronic configuration as the $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Phi$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}\Pi$ states. We have recently found that the $X5\Pi$ state is also perturbed, probably by a $\mathrm{<mrow\; data-mjx-texclass="ORD">7</mrow>}\Sigma +$ state $(3d\delta 23d\pi 23d\sigma 14s\sigma 1)$. In total, we have evidence for at least seven electronic states lying below $11000cm-1$ and possibly as many as nine.