Excitation modes for fourier transform-ion cyclotron resonance mass spectrometry

Schweikhard, L.; Marshall, Alan G.

doi:10.1016/1044-0305(93)80001-f

Cited by 103 publications

(79 citation statements)

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“…A phase difference of is introduced between the supplies to adjacent segments. The quadrupole field allows energy to be coupled between the modified cyclotron and magnetron motions [8]. With the additional presence of suitable damping, the radius of the magnetron motion decays, leaving the ions axialized.…”

Section: Volume 89 Number 9 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 99%

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Axialization of Laser Cooled Magnesium Ions in a Penning Trap

Powell

Segal²,

Thompson³

2002

Phys. Rev. Lett.

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We report the first demonstration of the axialization of laser cooled ions in a Penning trap. Axialization involves the application of a small radial quadrupole drive which couples the cyclotron and magnetron motions. This enhances the laser cooling, allowing tighter confinement of the ions to the central axis of the trap than is otherwise possible. Using an intensified charge-coupled device (ICCD) camera we have imaged the axialization process for the first time. For a single ion, we recorded a large decrease of the magnetron amplitude corresponding to a reduction in ion temperature of approximately 2 orders of magnitude to an upper limit of order 10 mK. We have discovered dynamics specific to the laser cooled system which depend critically on the axial drive frequency and amplitude. DOI: 10.1103/PhysRevLett.89.093003 PACS numbers: 32.80.Pj, 03.67.Lx, 41.20.-q, 42.50.Vk With the growing interest in quantum information processing there has been an increasing need to develop technology which might enable the implementation of the ideas proposed. The uniquely stable and isolated environment of the ion trap makes it an ideal tool for the investigation of quantum phenomena; indeed, ion traps have been placed at the forefront of advances in the area of quantum information science [1]. Recent experiments include the entanglement of four trapped ions, the building of a CNOT gate and quantum state engineering using a single particle [2][3][4].Very low temperatures can be reached in ion traps using laser cooling, but the minimum temperature can be limited by the nature of the trapping method itself. The two most widely used types of ion trap are the Paul (radio frequency) trap and the Penning trap [5]. For radial confinement, the former uses an electric field oscillating at a radio frequency, while the latter uses a static magnetic field. This means that in the Paul trap the ion motion is simple harmonic in all directions but in the radial plane of the Penning trap the action of the combined electric and magnetic fields results in a more complex orbital motion: a superposition of two rotations, the magnetron and the cyclotron rotations.Until now much work in the area of quantum information science has focused on the use of linear Paul traps which allow the preparation of stationary strings of ions and strong confinement to the Lamb-Dicke regime [1]. Unfortunately, the low temperature limit of the Paul trap can be affected by the ''micromotion'' of the trapped ions, which arises as a result of the trapping field and cannot be completely avoided. The Penning trap has no such limitation [5]. However, the nature of the motion in the radial plane of the Penning trap complicates the laser cooling process [6,7]. Specifically, it is difficult to achieve small magnetron radii. Problems arise because the magnetron motion is unstable: its total energy is negative so energy must be supplied in order to reduce the magnetron radius.Three frequencies govern the motion of ions in a Penning trap. The first is ! z , which describes th...

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Section: Volume 89 Number 9 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 99%

“…0 c 557 kHz. Axialization is the process by which particles in a Penning trap are driven towards the central axis of the trap [8]. It occurs when the efficient cooling of the cyclotron motion is effectively extended to the magnetron motion by coupling between the two induced by a weak external field oscillating at the true cyclotron frequency, !…”

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confidence: 99%

Axialization of Laser Cooled Magnesium Ions in a Penning Trap

Powell

Segal²,

Thompson³

2002

Phys. Rev. Lett.

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“…These voltages may be static or time dependent, most often they are periodic like cos ω d t, with the driving frequency ν d = ω d /2π chosen to suit the intended purpose. For experimental details we refer to the literature [10,15,16]. For the theoretical treatment it is important that the sources of these additional fields are on the electrode surfaces, while the trap interior is free of sources.…”

Section: Interaction With the External Quadrupole Fieldmentioning

confidence: 99%

“…As described in a preceding section, the operators x, y,ẋ, andẏ are related to the annihilation and creation operators a ± and a † ± by Eqs. (16), (17), (19), and (20). Taking the expectation value of these equations for a coherent state |α + (0), α − (0) , using Eq.…”

Section: Ramsey Excitation In Terms Of Classical Trajectoriesmentioning

confidence: 99%

The Ramsey method in high-precision mass spectrometry with Penning traps: Theoretical foundations

Kretzschmar

2007

International Journal of Mass Spectrometry

161

171

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This paper presents in a quantum mechanical framework a theoretical description of the interconversion of the magnetron and modified cyclotron motional modes of ions in a Penning trap due to excitation by external rf-quadrupole fields with a frequency near the true cyclotron frequency. The work aims at a correct description of the resonance line shapes that are observed in connection with more complicated excitation schemes using several excitation pulses, such as Ramsey's method of separated oscillating fields. Quantum mechanical arguments together with the "rotating wave approximation" suggest a model Hamiltonian that permits a rigorous solution of the corresponding Heisenberg equations of motion. We show that the ion motion in a Penning trap with an additional rf-quadrupole field is dynamically analogous to nuclear-magnetic-resonance. This is done by introducing the concept of the "Bloch vector operator", which is a vector operator obeying the commutation rules of an angular momentum operator and which is the analogue of a nuclear spin. During the quadrupole excitation the expectation value of the Bloch vector operator, which is an ordinary real three-vector, performs a precessional and nutational motion similar to the spin in nuclear-magnetic-resonance experiments. The frequency of the interconversion of the magnetron and modified cyclotron motional modes of the ions is the analogue of the Rabi frequency. Hence the applicability of Ramsey's ideas to Penning trap physics becomes understandable. Resonance line shapes are deduced from the general solution of the dynamical problem for arbitrary values of the excitation time, pulse structure and detuning of the quadrupole radiation. Results are given for excitation schemes with up to five pulses. A comparison of the theoretical results to experimental data is found in the accompanying paper by George et al. [S. George, et al., IJMS, this issue].

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“…It may be noted, that there is a second, closely related method to distinguish the polarity of simultaneously stored ions, namely by the application of quadrature (i.e., circularly-polarized) excitation [10,11]. In this case only ions of one polarity, either the cations or the anions, are excited and thus only their FT-ICR signal appears in conventional dipolar detection.…”

Section: Icrmentioning

confidence: 99%

Quadrature detection for the separation of the signals of positive and negative ions in fourier transform ion cyclotron resonance mass spectrometry

Schweikhard¹,

Drader²,

Shi³

et al. 2002

AIP Conference Proceedings

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Abstract. Positive and negative ions may be confined simultaneously in a nested open cylindrical Malmberg-Penning trap. However, ion charge sign cannot be distinguished by conventional dipolar (linearly-polarized) detection with a single pair of opposed electrodes. Here, the signals from each of two orthogonal pairs of opposed detection electrodes are acquired simultaneously and stored as real and imaginary parts of mathemetically complex data. Complex Fourier transformation yields separate spectra for positive and negative ions. For a fullerene sample, experimental quadrature detection yields C 60 + and C 60 -signals separated by -1440 u rather than by the mass of two electrons, -0.001 u in conventional dipolar detection.

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Excitation modes for fourier transform-ion cyclotron resonance mass spectrometry

Cited by 103 publications

References 73 publications

Axialization of Laser Cooled Magnesium Ions in a Penning Trap

Axialization of Laser Cooled Magnesium Ions in a Penning Trap

The Ramsey method in high-precision mass spectrometry with Penning traps: Theoretical foundations

Quadrature detection for the separation of the signals of positive and negative ions in fourier transform ion cyclotron resonance mass spectrometry

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