The capability of manipulating neutral atoms with the force of resonant scattered laser light is being exploited in several different areas of research. The author discusses applications in particle and nuclear physics by expediting some measurements of the subtle effects of the fundamental weak interaction in atoms and nuclei. It was shown in two recent experiments that it is possible to efficiently cool accelerator produced short-lived isotopes and load them into magneto-optic traps. These demonstrations open up new possibilities for obtaining the required precision in experiments involving rare radioactive isotopes.
We present studies of resonance-enhanced photoionization for isotope-selective loading of
Ca+ into a Paul trap. The ${4s}^{2}{}^{1}{S}_{0}\ensuremath{\leftrightarrow}4s4p{}^{1}{P}_{1}$ transition of neutral calcium is driven by a 423 nm laser and the atoms are photoionized by a second laser at 389 nm. Isotope selectivity is achieved by using crossed atomic and laser beams to reduce the Doppler width significantly below the isotope shifts in the 423 nm transition. The loading rate of ions into the trap is studied under a range of experimental parameters for the abundant isotope
40Ca+. Using the fluorescence of the atomic beam at 423 nm as a measure of the Ca number density, we estimate a lower limit for the absolute photoionization cross section of 170(60) Mb. We achieve loading and laser cooling of all the naturally occurring isotopes, without the need for enriched sources. Laser heating/cooling is observed to enhance the isotope selectivity. In the case of the rare species
43Ca+ and
46Ca+, which have not previously been laser cooled, the loading is not fully isotope selective, but we show that pure crystals of
43Ca+ may nevertheless be obtained. We find that for loading
40Ca+ the 389 nm laser may be replaced by an incoherent source.