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Title: Crystallization of Ca{sup +} ions in a linear rf octupole ion trap

Abstract

A laser-cooling experiment with Ca{sup +} ions trapped in a linear rf octupole ion trap is presented. The phase transition of the laser-cooled Ca{sup +} ions from the cloud to the crystal state is observed by an abrupt dip of the laser-induced fluorescence spectrum and indicates that mK temperatures are obtained. We have also performed molecular dynamics simulations under various conditions to confirm this property by deducing axially symmetric structures of Coulomb crystals and by evaluating the translational temperatures of the laser-cooled ions. The simulation results show that for small numbers of ions novel ring-shaped crystals are produced. As the number of ions is increased, cylindrical layers in the ring crystal are sequentially formed. For more than 100 ions, also hexagonal and spiral structures emerge in parts of the large-size ion crystal, which has a length on the order of millimeters for the present geometrical arrangement and voltages. An advantage of the linear rf octupole trap is its large almost-field-free region in the middle of the trap, where the micromotion amplitude is small for trapped ions. These results demonstrate that such a multipole trap has attractive features for quantum computing and ultracold ion-atom collision studies.

Authors:
; ; ; ; ;  [1];  [2];  [3];  [4]
  1. Department of Physics, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo 102-8554 (Japan)
  2. (Japan)
  3. (United States)
  4. (ILS), University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo, 182-8585 (Japan)
Publication Date:
OSTI Identifier:
20982357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.75.033409; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; AXIAL SYMMETRY; CALCIUM IONS; CRYSTALLIZATION; CYLINDRICAL CONFIGURATION; ELECTRIC POTENTIAL; FLUORESCENCE; FLUORESCENCE SPECTROSCOPY; ION-ATOM COLLISIONS; IONIC CRYSTALS; LASER RADIATION; MOLECULAR DYNAMICS METHOD; MOLECULAR STRUCTURE; OCTUPOLES; PHASE TRANSFORMATIONS; PHOTON-ATOM COLLISIONS; QUANTUM COMPUTERS; TEMPERATURE RANGE 0000-0013 K; TRAPPING; TRAPS

Citation Formats

Okada, Kunihiro, Yasuda, Kazuhiro, Takayanagi, Toshinobu, Wada, Michiharu, Schuessler, Hans A., Ohtani, Shunsuke, Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Department of Physics, Texas A and M University, College Station, Texas 77843, and Institute for Laser Science. Crystallization of Ca{sup +} ions in a linear rf octupole ion trap. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.033409.
Okada, Kunihiro, Yasuda, Kazuhiro, Takayanagi, Toshinobu, Wada, Michiharu, Schuessler, Hans A., Ohtani, Shunsuke, Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Department of Physics, Texas A and M University, College Station, Texas 77843, & Institute for Laser Science. Crystallization of Ca{sup +} ions in a linear rf octupole ion trap. United States. doi:10.1103/PHYSREVA.75.033409.
Okada, Kunihiro, Yasuda, Kazuhiro, Takayanagi, Toshinobu, Wada, Michiharu, Schuessler, Hans A., Ohtani, Shunsuke, Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Department of Physics, Texas A and M University, College Station, Texas 77843, and Institute for Laser Science. Thu . "Crystallization of Ca{sup +} ions in a linear rf octupole ion trap". United States. doi:10.1103/PHYSREVA.75.033409.
@article{osti_20982357,
title = {Crystallization of Ca{sup +} ions in a linear rf octupole ion trap},
author = {Okada, Kunihiro and Yasuda, Kazuhiro and Takayanagi, Toshinobu and Wada, Michiharu and Schuessler, Hans A. and Ohtani, Shunsuke and Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 and Department of Physics, Texas A and M University, College Station, Texas 77843 and Institute for Laser Science},
abstractNote = {A laser-cooling experiment with Ca{sup +} ions trapped in a linear rf octupole ion trap is presented. The phase transition of the laser-cooled Ca{sup +} ions from the cloud to the crystal state is observed by an abrupt dip of the laser-induced fluorescence spectrum and indicates that mK temperatures are obtained. We have also performed molecular dynamics simulations under various conditions to confirm this property by deducing axially symmetric structures of Coulomb crystals and by evaluating the translational temperatures of the laser-cooled ions. The simulation results show that for small numbers of ions novel ring-shaped crystals are produced. As the number of ions is increased, cylindrical layers in the ring crystal are sequentially formed. For more than 100 ions, also hexagonal and spiral structures emerge in parts of the large-size ion crystal, which has a length on the order of millimeters for the present geometrical arrangement and voltages. An advantage of the linear rf octupole trap is its large almost-field-free region in the middle of the trap, where the micromotion amplitude is small for trapped ions. These results demonstrate that such a multipole trap has attractive features for quantum computing and ultracold ion-atom collision studies.},
doi = {10.1103/PHYSREVA.75.033409},
journal = {Physical Review. A},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Ion Coulomb crystals of laser-cooled Ca{sup +} ions have been observed in a cryogenic linear octupole rf ion trap for the first time. Due to the almost field-free central region, large ion crystals containing over 10{sup 4} ions of millimeter size were successfully produced. The shapes of the crystals can be manipulated by changing the static voltages applied to the octupole rods and the endcap electrodes. Quasi-two-dimensional Coulomb crystals consisting of a small number of ions were also observed with single-ion sensitivity. When a large number of ions is crystallized in the octupole trap, a new kind crystal image withmore » a dip along the axial direction was obtained. The results show that a linear octupole trap and multipole traps are available for producing large, cold, and novel ion Coulomb crystals. The planar ring-type crystal which has not been observed before may lead to future interesting applications.« less
  • Fluorescence line profiles and their implications on the cooling dynamics of the Mg{sup +} ions stored in a linear rf trap are studied. The line profile is dictated by the temperature of the ion cloud at different laser detunings. The upper bound of the lowest temperature was estimated for different values of the rf trapping potential amplitude and the buffer gas pressure. A general trend of this ultimate temperature to increase with the rf trapping voltage and buffer gas pressure is expected, with an abrupt change at some critical value corresponding to the transition to and from a strongly correlatedmore » liquid or crystal state. While on the one hand this expectation was confirmed when the buffer gas pressure was varied; on the other hand the influence of the amplitude of the trapping voltage on the ultimate temperature shows an interesting new feature of first dipping down before the sharp increase occurs.« less
  • A large sample (N{approx_equal}10{sup 4}) of fullerene ions (m=720 a.u) is cooled by means of a much smaller number({approx_equal}100) of laser-cooled magnesium ions (m=24 a.u). The results demonstrate that sympathetic cooling of large molecules to low temperatures is feasible. The temperature of the {sup 24}Mg{sup +} ions in the mixed Mg{sup +}-C{sub 60}{sup +} ion cloud stored in an rf trap is found to be T{sub Mg}=5 K from their fluorescence signal. Molecular dynamics simulations are used to obtain the corresponding equilibrium temperature of the fullerene ions, and show that T{sub C{sub 60}}=14 K.
  • The parametric resonant behavior of ions inside a linear rf ion trap is studied both theoretically and experimentally. Theoretically, the resonant motion of ions inside an ideal ion trap is described by approximating the trapping rf field as a harmonic pseudopotential with the ions being excited by an additional quadrupolar ac voltage. The resulting damped Mathieu equation is studied and the regions of resonant instability are predicted by investigating the solutions. Experimentally, the parametric excitation of Mg{sup +} ions is observed by subjecting the cloud of trapped ions to an additional quadrupolar ac field. The various ion motion resonances aremore » detected through the disappearance of the laser-induced fluorescence signal. Weak damping is introduced by the presence of a low-pressure buffer gas. The experimental results are compared with the theoretical predictions.« less
  • Measurement of isotope ratios of Calcium is very useful in many fields. So we demonstrated the measurement of isotope ratios of {sup 40}Ca{sup +}(abundance 96.4%) to {sup 44}Ca{sup +}(2.09%) ions in a linear Paul trap with several laser lights tuning to the isotope shifts. And we found that the experimental parameters had large influences on the measurement of the isotope ratios.