Knowledge Bank

The emission spectrum of $F2$ has been investigated under high resolution in the region 4800-8000 {\AA} and the so-called orange system has been analyzed in detail. Rotational analyses have been made of nine bands and some features of six others have been observed. These fifteen bands involve eight vibrational levels of a $B\prime \mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi$ state, one level of a $B\prime \mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi$ state, and two levels of a $C\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ state. These levels are connected by the electronic transitions $C\to B$ and $C\to B1$. The spectrum is marked by extensive perturbations. All rotational levels in the B state are broadened, some greatly, and the broadening varies from band to band but appears to be constant within a band. Furthermore only two vibrational states have been observed in which the position of the rotational levels are not perturbed. These unusual spectral features will be illustrated and discussed, and molecular constants will be given. Brief mention will also be made of additional bands at the blue end of the region which have been attributed to $F2+$.