IONIZATION-POTENTIALS OF CAF AND BAF

Although the alkaline earth-monohalide compounds, MX, have been extens ively studied, their ionization potentials to MX+ are only known to wi thin a few tenths of an eV. Using an improved electron impact ionizati on potential measurement to assist in arranging spectroscopic vibronic band origins into Rydberg series, we report high precision ionization potential measurements for CaF and BaF to be IP(CaF) = 5.8270 +/- 0.0 006 eV and IP(BaF) = 4.8034 +/- 0.0004 eV. The synergism between the e lectron impact method and the spectroscopic method is detailed, and th e minimum accuracy required of the electron impact data is assessed.