Isotope-selective trapping of rare calcium ions using high-power incoherent light sources for the second step of photo-ionization
Rare calcium isotope 48Ca+ (0.187%) has been selectively loaded in a linear Paul trap using two ultraviolet light emitting diodes with the output power of 85 mW for the second excitation in a two-step photo-ionization process. Isotope selectivity has been achieved by utilizing the isotope shifts for the 4s2 1 S 0–4s4p1 P 1 transition of neutral calcium atom. Sympathetic cooling of 48Ca+ ions has been demonstrated using 40Ca+ ions as refrigerant ions. Purification of rare isotope 42Ca+ ions (0.647%) from a mixture of 40Ca+ (96.9%) and 42Ca+ ions has been performed by adjusting the detuning of the cooling laser frequency, which overcomes the imperfect selectivity for some rare isotopes having close resonance frequencies to that of 40Ca in the 4s2 1 S 0–4s4p1 P 1 transition. The methods can be applied to 43Ca+ ion (0.135%) that has been considered as one of the attractive candidates for quantum information processing as well as for an optical frequency standard.
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