314 research outputs found
Ellipsoidal Coulomb Crystals in a Linear Radiofrequency Trap
A static quadrupole potential breaks the cylindrical symmetry of the
effective potential of a linear rf trap. For a one-component fluid plasma at
low temperature, the resulting equilibrium charge distribution is predicted to
be an ellipsoid. We have produced laser-cooled Be ellipsoidal ion crystals
and found good agreement between their shapes and the cold fluid prediction. In
two-species mixtures, containing Be and sympathetically cooled ions of
lower mass, a sufficiently strong static quadrupole potential produces a
spatial separation of the species.Comment: 4 pages, 3 figure
Ion-neutral sympathetic cooling in a hybrid linear rf Paul and magneto-optical trap
Long range polarization forces between ions and neutral atoms result in large
elastic scattering cross sections, e.g., 10^6 a.u. for Na+ on Na or Ca+ on Na
at cold and ultracold temperatures. This suggests that a hybrid ion-neutral
trap should offer a general means for significant sympathetic cooling of atomic
or molecular ions. We present SIMION 7.0 simulation results concerning the
advantages and limitations of sympathetic cooling within a hybrid trap
apparatus, consisting of a linear rf Paul trap concentric with a Na
magneto-optical trap (MOT). This paper explores the impact of various heating
mechanisms on the hybrid system and how parameters related to the MOT, Paul
trap, number of ions, and ion species affect the efficiency of the sympathetic
cooling
Coulomb crystal mass spectrometry in a digital ion trap
We present a mass spectrometric technique for identifying the masses and relative abundances of Coulomb-crystallized ions held in a linear Paul trap. A digital radio-frequency wave form is employed to generate the trapping potential, as this can be cleanly switched off, and static dipolar fields are subsequently applied to the trap electrodes for ion ejection. Close to 100% detection efficiency is demonstrated for Ca+ and CaF+ ions from bicomponent Ca+ â CaF+ Coulomb crystals prepared by the reaction of Ca+ with CH3F. A quantitative linear relationship is observed between ion number and the corresponding integrated time-of-flight (TOF) peak, independent of the ionic species. The technique is applicable to a diverse range of multicomponent Coulomb crystalsâdemonstrated here for Ca+ â NH3+ â NH4+ and Ca+ â CaOH+ â CaOD+ crystalsâand will facilitate the measurement of ion-molecule reaction rates and branching ratios in complicated reaction systems
Evidence of sympathetic cooling of Na+ ions by a Na MOT in a hybrid trap
A hybrid ion-neutral trap provides an ideal system to study collisional
dynamics between ions and neutrals. This system provides a general cooling
method that can be applied to optically inaccessible species and can also
potentially cool internal degrees of freedom. The long range polarization
potentials () between ions and neutrals result in large
scattering cross sections at cold temperatures, making the hybrid trap a
favorable system for efficient sympathetic cooling of ions by collisions with
neutral atoms. We present experimental evidence of sympathetic cooling in a
hybrid trap of \ce{Na+} ions, which are closed shell and therefore do not have
a laser induced atomic transition, by equal mass cold Na atoms in a
magneto-optical trap (MOT).Comment: 7 figure
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