Bulletin of the American Physical Society

Two-photon photo-ionization of the Ca $4s3d \; ^1D_2$ level in an optical dipole trap

Elizabeth A. Cummings, J. E. Daily, Dallin Durfee, Scott Bergeson, Ralf Gommers

Published May 18, 2005• 0 citations

Abstract

We report an optical dipole trap for calcium. The trap is created by focusing a 488-nm argon-ion laser beam into a calcium magneto-optical trap. The argon-ion laser photoionizes atoms in the trap because of a near-resonance with the 4s4f 1^F3 level. By measuring the dipole-trap decay rate as a function of argon-ion laser intensity, we determine the 1^F3 photoionization cross section at our wavelength to be approximately 230 Mb.

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Bulletin of the American Physical Society

Two-photon photo-ionization of the Ca $4s3d \; ^1D_2$ level in an optical dipole trapTwo-photon photo-ionization of the Ca $4s3d \; ^1D_2$ level in an optical dipole trap

Elizabeth A. Cummings, J. E. Daily, Dallin Durfee, Scott Bergeson, Ralf Gommers

Published May 18, 2005• 0 citations

OpenAlex

Abstract

Related papers

Two-photon photoionization of the Ca 4s3dD21 level in an optical dipole trap

J. E. Daily, Ralf Gommers, Elizabeth A. Cummings +2 more

We report an optical dipole trap for calcium. The trap is created by focusing a $488\text{\ensuremath{-}}\mathrm{nm}$ argon-ion laser beam into a calcium magneto-optical trap. The argon-ion laser photoionizes atoms in the trap because of a near-resonance with the $4s4f\phantom{\rule{0.2em}{0ex}}^{1}F_{3}$ level. By measuring the dipole-trap decay rate as a function of argon-ion laser intensity, we determine the $^{1}F_{3}$ photoionization cross section at our wavelength to be approximately $230\phantom{\rule{0.3em}{0ex}}\mathrm{Mb}$ .We report an optical dipole trap for calcium. The trap is created by focusing a $488\text{\ensuremath{-}}\mathrm{nm}$ argon-ion laser beam into a calcium magneto-optical trap. The argon-ion laser photoionizes atoms in the trap because of a near-resonance with the $4s4f\phantom{\rule{0.2em}{0ex}}^{1}F_{3}$ level. By measuring the dipole-trap decay rate as a function of argon-ion laser intensity, we determine the $^{1}F_{3}$ photoionization cross section at our wavelength to be approximately $230\phantom{\rule{0.3em}{0ex}}\mathrm{Mb}$.

arXiv:physics/0411004Physical Review AApr 19, 20052 citations

Two-Photon Ionization of the Calcium 4S3D 1D2 Level in an Optical Dipole Trap

J. E. Daily

This thesis reports an optical dipole trap for atomic calcium. The dipole trap is loaded from a magneto-optical trap (MOT) of calcium atoms cooled near the Doppler limit (~1 mK). The dipole trap is formed by a large-frame argon ion laser focused to 20 microns into the center of the MOT. This laser runs single-line at 488 nm with a maximum power of 10.6 watts. These parameters result in a trap of 125 mK for calcium atoms in the 4s3d 1D2 state. The 488 nm light also photo-ionizes the trapped atoms due to a near-resonant transition to the 4s4f 1F3 level. These ions leave the trap and are detected to determine the trap decay rate. By measuring this decay rate as a function of 488 nm intensity, we determine the 1F3 photo-ionization cross section at this wavelength to be approximately 230 Mb.This thesis reports an optical dipole trap for atomic calcium. The dipole trap is loaded from a magneto-optical trap (MOT) of calcium atoms cooled near the Doppler limit (~1 mK). The dipole trap is formed by a large-frame argon ion laser focused to 20 microns into the center of the MOT. This laser runs single-line at 488 nm with a maximum power of 10.6 watts. These parameters result in a trap of 125 mK for calcium atoms in the 4s3d 1D2 state. The 488 nm light also photo-ionizes the trapped atoms due to a near-resonant transition to the 4s4f 1F3 level. These ions leave the trap and are detected to determine the trap decay rate. By measuring this decay rate as a function of 488 nm intensity, we determine the 1F3 photo-ionization cross section at this wavelength to be approximately 230 Mb.

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Isotope-selective photoionization for calcium ion trapping

D. Lucas, A. Ramos, Jonathan Home +6 more

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.

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Two-photon ionization of cold rubidium atoms

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Two-photon ionization cross sections from the rubidium ground state have been measured with both a cw 421-nm laser and a combination of cw 421- and 1002-nm lasers. The measurements were performed within a high-vacuum magneto-optical trap while the trapping lasers were switched off, exploiting the long trap lifetime and also the trap laser confinement. The two-photon cross sections were determined for the blue laser near resonance with the 6P1/2 and 6P3/2 states and compared with the estimates of a theoretical model. In near resonance with the 6P states, large two-photon photoionization cross sections were measured.Two-photon ionization cross sections from the rubidium ground state have been measured with both a cw 421-nm laser and a combination of cw 421- and 1002-nm lasers. The measurements were performed within a high-vacuum magneto-optical trap while the trapping lasers were switched off, exploiting the long trap lifetime and also the trap laser confinement. The two-photon cross sections were determined for the blue laser near resonance with the 6P1/2 and 6P3/2 states and compared with the estimates of a theoretical model. In near resonance with the 6P states, large two-photon photoionization cross sections were measured.

Journal of the Optical Society of America BMar 1, 200412 citations

Laser spectroscopy of the 4s4p 3P2 – 4s3d 1D2 transition on magnetically trapped calcium atoms

Umakanth Dammalapati, I. Norris, C. Burrows +1 more

Laser excitation of the $4s4p {}^{3}{P}_{2} -- 4s3d {}^{1}{D}_{2}$ transition in atomic calcium has been observed and the wavelength determined to 1530.5298(6) nm. The metastable $4s4p {}^{3}{P}_{2}$ atoms were magnetically trapped in the quadrupole magnetic field of a magneto-optical trap. This state represents the only ``loss'' channel for the calcium atoms when laser cooled on the $4{s}^{2} {}^{1}{S}_{0} -- 4s4p {}^{1}{P}_{1}$ transition. A rate equation model shows that an order of magnitude more atoms are trapped in this state compared with those taking part in the main cooling cycle. Excitation of the ${}^{3}{P}_{2}$ atoms back up to the $4s3d {}^{1}{D}_{2}$ state provides a means of accessing these atoms. Efficient repumping is achieved if the 1530-nm laser is used in conjunction with a 672-nm laser driving the $4s3d {}^{1}{D}_{2} -- 4s5p {}^{1}{P}_{1}$ transition. In the present experiment, we detected about $4.5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ trapped ${}^{3}{P}_{2}$ atoms, a relatively low atom density, and measured a lifetime of approximately 1 s, which is limited by background collisions.Laser excitation of the $4s4p {}^{3}{P}_{2} -- 4s3d {}^{1}{D}_{2}$ transition in atomic calcium has been observed and the wavelength determined to 1530.5298(6) nm. The metastable $4s4p {}^{3}{P}_{2}$ atoms were magnetically trapped in the quadrupole magnetic field of a magneto-optical trap. This state represents the only ``loss'' channel for the calcium atoms when laser cooled on the $4{s}^{2} {}^{1}{S}_{0} -- 4s4p {}^{1}{P}_{1}$ transition. A rate equation model shows that an order of magnitude more atoms are trapped in this state compared with those taking part in the main cooling cycle. Excitation of the ${}^{3}{P}_{2}$ atoms back up to the $4s3d {}^{1}{D}_{2}$ state provides a means of accessing these atoms. Efficient repumping is achieved if the 1530-nm laser is used in conjunction with a 672-nm laser driving the $4s3d {}^{1}{D}_{2} -- 4s5p {}^{1}{P}_{1}$ transition. In the present experiment, we detected about $4.5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ trapped ${}^{3}{P}_{2}$ atoms, a relatively low atom density, and measured a lifetime of approximately 1 s, which is limited by background collisions.

Physical Review AJun 27, 20112 citations

Measurement of the photoionization cross section of the 6P3/2 state of cesium

Brian M. Patterson, T. Takekoshi, R. J. Knize

We report the measurement of the absolute photoionization cross section for the ${6P}_{3/2}$ state of cesium. Cross sections were determined by measuring the photoionization rate of cesium atoms confined in a magneto-optical trap. The photoionization rate was measured by monitoring the decay of trap fluorescence during exposure to ionizing laser radiation. The measurements were made in the wavelength range 457.9 to 501.7 nm using several lines from an Ar-ion laser. Our results are compared to other experimental measurements as well as to existing theories.We report the measurement of the absolute photoionization cross section for the ${6P}_{3/2}$ state of cesium. Cross sections were determined by measuring the photoionization rate of cesium atoms confined in a magneto-optical trap. The photoionization rate was measured by monitoring the decay of trap fluorescence during exposure to ionizing laser radiation. The measurements were made in the wavelength range 457.9 to 501.7 nm using several lines from an Ar-ion laser. Our results are compared to other experimental measurements as well as to existing theories.

Physical Review AMar 1, 199934 citations

Two-photon photo-ionization of the Ca

4s3d \; ^1D_2

level in an optical dipole trap

4s4f\phantom{\rule{0.2em}{0ex}}^{1}F_{3}

level. By measuring the dipole-trap decay rate as a function of argon-ion laser intensity, we determine the

^{1}F_{3}

photoionization cross section at our wavelength to be approximately

230\phantom{\rule{0.3em}{0ex}}\mathrm{Mb}

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.

Laser excitation of the

4s4p {}^{3}{P}_{2} -- 4s3d {}^{1}{D}_{2}

transition in atomic calcium has been observed and the wavelength determined to 1530.5298(6) nm. The metastable

4s4p {}^{3}{P}_{2}

atoms were magnetically trapped in the quadrupole magnetic field of a magneto-optical trap. This state represents the only ``loss'' channel for the calcium atoms when laser cooled on the

4{s}^{2} {}^{1}{S}_{0} -- 4s4p {}^{1}{P}_{1}

transition. A rate equation model shows that an order of magnitude more atoms are trapped in this state compared with those taking part in the main cooling cycle. Excitation of the

{}^{3}{P}_{2}

atoms back up to the

4s3d {}^{1}{D}_{2}

state provides a means of accessing these atoms. Efficient repumping is achieved if the 1530-nm laser is used in conjunction with a 672-nm laser driving the

4s3d {}^{1}{D}_{2} -- 4s5p {}^{1}{P}_{1}

transition. In the present experiment, we detected about $4.5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ trapped

{}^{3}{P}_{2}

atoms, a relatively low atom density, and measured a lifetime of approximately 1 s, which is limited by background collisions.

We report the measurement of the absolute photoionization cross section for the

{6P}_{3/2}

state of cesium. Cross sections were determined by measuring the photoionization rate of cesium atoms confined in a magneto-optical trap. The photoionization rate was measured by monitoring the decay of trap fluorescence during exposure to ionizing laser radiation. The measurements were made in the wavelength range 457.9 to 501.7 nm using several lines from an Ar-ion laser. Our results are compared to other experimental measurements as well as to existing theories.