Laser cooling, trapping and spectroscopy of calcium isotopes

We present studies of resonance-enhanced photoionization for isotope-selective loading of ${\mathrm{Ca}}^{+}$ 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 ${}^{40}{\mathrm{Ca}}^{+}.$ 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 ${}^{43}{\mathrm{Ca}}^{+}$ and ${}^{46}{\mathrm{Ca}}^{+},$ which have not previously been laser cooled, the loading is not fully isotope selective, but we show that pure crystals of ${}^{43}{\mathrm{Ca}}^{+}$ may nevertheless be obtained. We find that for loading ${}^{40}{\mathrm{Ca}}^{+}$ the 389 nm laser may be replaced by an incoherent source.We present studies of resonance-enhanced photoionization for isotope-selective loading of ${\mathrm{Ca}}^{+}$ 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 ${}^{40}{\mathrm{Ca}}^{+}.$ 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 ${}^{43}{\mathrm{Ca}}^{+}$ and ${}^{46}{\mathrm{Ca}}^{+},$ which have not previously been laser cooled, the loading is not fully isotope selective, but we show that pure crystals of ${}^{43}{\mathrm{Ca}}^{+}$ may nevertheless be obtained. We find that for loading ${}^{40}{\mathrm{Ca}}^{+}$ the 389 nm laser may be replaced by an incoherent source.

arXiv:physics/0310044Physical Review AJan 1, 2004163 citations

Saturated absorption spectroscopy of calcium in a hollow-cathode lamp

Umakanth Dammalapati, I Norris, Erling Riis

We report on a technique for obtaining dispersive saturated absorption features by two pump beams derived from an acousto-optic modulator. One of the beams is frequency shifted by the modulator allowing for a variable frequency offset of the resulting signal. They are used to saturate the atomic transition in the low-density vapour of the lamp. The sensitivity of the technique is sufficient to observe clear signals from isotopes of calcium unresolved by the inhomogeneous broadening and with natural abundances of less than 0.2%. The technique is used for offset locking the frequency of a Ti:Sapphire laser used for laser cooling and trapping of calcium.We report on a technique for obtaining dispersive saturated absorption features by two pump beams derived from an acousto-optic modulator. One of the beams is frequency shifted by the modulator allowing for a variable frequency offset of the resulting signal. They are used to saturate the atomic transition in the low-density vapour of the lamp. The sensitivity of the technique is sufficient to observe clear signals from isotopes of calcium unresolved by the inhomogeneous broadening and with natural abundances of less than 0.2%. The technique is used for offset locking the frequency of a Ti:Sapphire laser used for laser cooling and trapping of calcium.

Journal of Physics B Atomic Molecular and Optical PhysicsJul 20, 200921 citations

We present studies of resonance-enhanced photoionization for isotope-selective loading of

{\mathrm{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

{}^{40}{\mathrm{Ca}}^{+}.

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

{}^{43}{\mathrm{Ca}}^{+}

and

{}^{46}{\mathrm{Ca}}^{+},

which have not previously been laser cooled, the loading is not fully isotope selective, but we show that pure crystals of

{}^{43}{\mathrm{Ca}}^{+}

may nevertheless be obtained. We find that for loading

{}^{40}{\mathrm{Ca}}^{+}

the 389 nm laser may be replaced by an incoherent source.