Knowledge Bank

The emission spectrum of FeF has been observed in the near infrared region from $9000cm1$ to $12000cm-1$. The bands were excited in a high temperature carbon tube furnace and have been recorded using a Fourier transform spectrometer at a resolution of $0.02cm-1$. The observed bands have been assigned as the 0-1, 0-0, 1-0, and 2-0 bands of the $g4\Delta -a4\Delta$, transition, analogous to the $F4\Delta -X4\Delta$. transition of FeH at $1\mu$m. Each vibrational band consists of four sub-bands assigned as $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}\Delta 1/2-4\Delta 1/24\Delta 3/2-4\Delta 3/2,4\Delta 3/2-4\Delta 3/2$ and . The rotational analysis of these bands has been performed and molecular constants have been determined. This work represents the first observation of the $g4\Delta -a4\Delta$ transition of FeF. We discuss the correspondence between the low-lying electronic states of FeF, FeH and $Fe\ast$.