Knowledge Bank

The absorption spectra of gaseous $MoF6$ and $WF6$ have been measured between 2500 {\AA} and 1120 {\AA}, (40 000 - 89 000 $cm-1$). The bands of $WF6$ are displaced $\sim$ 10 000 $cm-1$ to higher energy than those of M0$F6$. The other spectral feature--the band separations, structures and relative intensities-- are almost identical. Because of this, the 5 observed transitions are interpreted as ligand-to-metal $t2g$ transitions. From the spectrum of $MoF6$ the ligand field splitting parameter of this molecule is estimated to be $>40000cm-1$, appreciably greater than anticipated.