Knowledge Bank

The absorption spectrum of the $F2$ molecule has been photographed in the third and fourth orders of a 10-m concave grating spectrograph. The resolution is sufficient to allow us to analyze the rotational structures of many bands and thus definitely identify some of the excited states. Prior to this work only low resolution spectra had been observed and even the ground state had been very poorly characterized. No Rydberg series have been identified as yet but from the rotational analysis of 25 bands the following points have been established. (1) From the analysis of ``hot’’ bands the following ground state constants have been determined; $\Delta G(12)=893.95$, $\Delta G(32)=870.05$, $B0=0.8827$, $\alpha =0.0131cm-1$. (2) The upper states of the visible emission bands have been identified as two $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ levels at 115 049.3 and 113 $939.9cm-1$ above the ground state. (3) The progression which has been used by Strickler and $Krauss1$ to determine the dissociation energy of $F2$ has been found to consist of bands which differ greatly in rotational structure, and it appears likely that the bands are strongly perturbed. The value of the dissociation energy determined by Strickler and $Krauss1$ therefore can not be considered reliable.