Molecular-dynamics simulations of cold single-species and multispecies ion ensembles in a linear Paul trap

Zhang, C. B.; Offenberg, D.; Roth, Bernhard; Wilson, Mark A.; Schiller, S.

doi:10.1103/physreva.76.012719

Cited by 86 publications

(125 citation statements)

References 29 publications

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“…In the presented form, LA-MS represents an easy-toimplement detection method in cold ion experiments that can be used complementarily to (and, perhaps, more robustly than) techniques based on analysing fluorescence images [38,[45][46][47][48] or mass spectrometry based on resonant excitation of the secular ion motion [26,49,50]. It is an ideal tool for spectroscopy of molecular ions and significantly outperforms previous implementations [51][52][53][54].…”

Section: Discussionmentioning

confidence: 99%

Laser-Cooling-Assisted Mass Spectrometry

et al. 2014

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Mass spectrometry is used in a wide range of scientific disciplines including proteomics, pharmaceutics, forensics, and fundamental physics and chemistry. Given this ubiquity, there is a worldwide effort to improve the efficiency and resolution of mass spectrometers. However, the performance of all techniques is ultimately limited by the initial phase-space distribution of the molecules being analyzed. Here, we dramatically reduce the width of this initial phase-space distribution by sympathetically cooling the input molecules with laser-cooled, co-trapped atomic ions, improving both the mass resolution and detection efficiency of a time-of-flight mass spectrometer by over an order of magnitude. Detailed molecular dynamics simulations verify the technique and aid with evaluating its effectiveness. Our technique appears to be applicable to other types of mass spectrometers.

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Section: Discussionmentioning

confidence: 99%

Laser-Cooling-Assisted Mass Spectrometry

et al. 2014

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“…We use molecular dynamics simulations to deduce ion numbers, three-dimensional spatial distributions and upper limits for the translational temperature of each species contained in the crystal from CCD (charge-coupled device) camera images of the ion ensembles. The simulations include full Coulomb interaction, light pressure forces, anisotropies of the trap pseudopotential and species-dependent heating rates 30 .…”

Section: Methodsmentioning

confidence: 99%

All-optical preparation of molecular ions in the rovibrational ground state

et al. 2010

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In the field of cold quantum matter, control of the motional degrees of freedom of both neutral and charged gas-phase molecules has been achieved for a wide range of species 1-11 . However, cooling of the internal degrees of freedom remains challenging. Recently, transfer to the internal ground state by sophisticated optical techniques has been demonstrated for neutral alkali dimers created in single quantum states from ultracold atoms 12-15 . Here we demonstrate cooling of the rotational degree of freedom of heteronuclear diatomic molecules with a thermal distribution of internal states, using a simple, robust and general optical-pumping scheme with two low-power continuous-wave lasers. With trapped and translationally cooled hydrogen deuteride (HD + ) molecular ions as a model system, we achieve 78(4)% rovibrational ground-state population. The rotationally, vibrationally and translationally cold molecular ion ensemble is suitable for a number of applications, such as generation of long-lived coherences or frequency metrology of fundamental constants 16,17 .The study of cold molecular systems promises new insights and advances in many fields of physics and physical chemistry. As in atomic physics, the key to tapping the full potential of molecules is the ability to accurately control the external and internal degrees of freedom of the particles. The complex internal structure of molecules has however so far precluded direct application of many techniques developed for trapping and cooling of atoms, demanding modified or completely new approaches. Now, a large toolbox for trapping and cooling the motional degrees of freedom of both neutral and charged molecules is available 18 . Although general schemes for cooling the internal degrees of freedom of molecules have been proposed 19,20 , the most general method available at present is cryogenic buffer-gas cooling, which is efficient only for molecules in the vibrational ground state and limits the translational temperature to a few hundred millikelvin 7 . Coherent transfer to the rovibrational ground state 11-14 is most suitable when most of the molecules are initially in the same quantum state, as is the case for molecules produced by associating cold atoms.For heteronuclear molecular ensembles for which the population is distributed among many rotational levels in the v = 0 vibrational manifold, optical pumping has been proposed as an approach to rotational cooling 21,22 . We demonstrate here that a scheme using two laser fields driving a fundamental and an overtone vibrational electric dipole transition 21 yields a large ground-state population and briefly discuss the applicability of the scheme to various diatomic molecular species. Figure 1 shows the energy levels (without hyperfine structure) and electric dipole transitions of the HD + molecule relevant for the experiment. The initial internal-state distribution is given by a Boltzmann distribution reflecting thermal equilibrium with the T ∼ = 300 K blackbody radiation field emitted by the experimental Inst...

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“…We therefore have a low density mesoscopic system which would be poorly described by mean-field methods so we cannot use NlogN approximate methods [17] for the Coulomb interaction and we have to exactly compute it using the N 2 all-pairs approach. We solve Newton's equations including the time-dependent confinement electric fields of the linear trap, the exact Coulomb force between all ion pairs and the laser interaction [18][19][20][21][22][23].…”

Section: Ion Crystal Dynamics Modelmentioning

confidence: 99%

\(\bar{\text{H}}^{+}\) Sympathetic Cooling Simulations with a Variable Time Step

Sillitoe

Karr

Heinrich

et al. 2017

Proceedings of the 12th International Conference on Low Energy Antiproton Physics (LEAP2016)

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In this paper we present a new variable time step criterion for the velocity-Verlet algorithm allowing to correctly simulate the dynamics of charged particles exchanging energy via Coulomb collisions while minimising simulation time. We present physical arguments supporting the use of the criterion along with numerical results proving its validity. We numerically show thatH + ions with 18 meV initial energy can be captured and sympathetically cooled by a Coulomb crystal of Be + and HD + in less than 10 ms, an important result for the GBAR project.

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Molecular-dynamics simulations of cold single-species and multispecies ion ensembles in a linear Paul trap

Cited by 86 publications

References 29 publications

Laser-Cooling-Assisted Mass Spectrometry

Laser-Cooling-Assisted Mass Spectrometry

All-optical preparation of molecular ions in the rovibrational ground state

\(\bar{\text{H}}^{+}\) Sympathetic Cooling Simulations with a Variable Time Step

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