Knowledge Bank

We have observed the pure rotational spectrum of the $SiF+$ ion in magnetically enhanced abnormal glow discharges in $SiF4/Ar$ mixtures. Transitions up to the $J-11-12$ near 500 -GHz were observed and used to determine the usual Dunham expansion constants for a diatomic molecule. The ion yields fairly intense spectra (comparable to those of $HCO+)$ and also has a fairly hot vibrational distribution. Thus we have been able to observe transitions for v = 0 to 12 for the main isotopic form and $v=0=3$ for $\mathrm{<mrow\; data-mjx-texclass="ORD">29</mrow>}SiF+$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">30</mrow>}SiF+$ so far. The spectrum was initially located by using our ab initio prediction of the structure at the $MP4$ level with a large basis $set.1$ We also used a quadrupole mass spectrometer system to optimize the production of $SiF+$ before beginning the search for the microwave spectrum.