Photoionization loading of barium ion traps.

We demonstrate a simple and effective technique for photoionization loading barium ions into a linear trap. Photoionization allows isotope selectivity, greater loading efficiency, and eliminates the charging of insulators in the trapping region, typical of electron impact ionization. Two-step photo-ionization of barium is accomplished using an intercombination line in neutral barium ($ 5s2 {}^1S_0 \rightarrow 6s6p {}^3P_1, \lambda = 791$ nm ) followed by excitation above the ionization threshold using a nitrogen gas laser ($ \lambda = 337$ nm). Isotopic selectivity is achieved by near doppler-free excitation of the triplet $6s6p {}^3P_1$ state. Application of the technique to a barium ion-trap cavity QED experiment will be discussed.