3D Trap Research Articles

On-chip generation of acoustical vortices with swirling surface acoustic waves for single particle manipulation and vorticity control

Surface acoustic waves (SAWs) are versatile tools for the manipulation of fluids at small scales. These waves can be used to displace, divide, merge, and atomize sessile droplets, but also actuate fluids embedded in microchannels. In this presentation, we will show that IDTs array and inverse filter technique enable on-chip synthesis of a new type of SAWs, called swirling SAWs, which degenerate into bulk acoustical vortices when transmitted to a liquid. These acoustical vortices can be tailored to create a 3D particle trap and thus selective single particle acoustical tweezers, with digital control of the trap position. They can also induce controlled vortical flows, whose topology essentially relies on the topology of the underlying acoustical vortex.

Twin trap or hyphenation of a 3D Paul- and a Cassinian ion trap.

A new, generalized form of electrostatic, harmonic ion trap mass analyzer, referred to as a Cassinian trap, was introduced in 2009. The present work couples a second order Cassinian trap with a 3D Paul trap in an effort to produce an instrument having the advantages of both (i.e., MS(n) and high mass resolution and accuracy). The present study demonstrates the trapping of ions in the 3D Paul trap and their subsequent transfer to the Cassinian trap. The simultaneous transfer of ions over a broad (factor of 13) mass range is shown. Once in the Cassinian trap, ions can be mass analyzed by Fourier transform means, producing resolving powers as high as 53,000 for the fundamental FID and 140,000 for the third harmonic in 1 s.

Low-temperature post-deposition annealing investigation for 3D charge trap flash memory by Kelvin probe force microscopy

The influence of post-deposition annealing (PDA) temperature condition on charge distribution behavior of HfO2 thin films was systematically investigated by various-temperature Kelvin probe force microscopy technology. Contact potential difference profiles demonstrated that charge storage capability shrinks with decreasing annealing temperature from 1,000 to 500 °C and lower. Compared to 1,000 °C PDA, it was found that 500 °C PDA causes deeper effective trap energy level, suppresses lateral charge spreading, and improves the retention characteristics. It is concluded that low-temperature PDA can be adopted in 3D HfO2-based charge trap flash memory to improve the thermal treatment compatibility of the bottom peripheral logic and upper memory arrays.

Trapping neutral atoms in the field of a vortex pinned by a superconducting nanodisk

Atom chips made of superconducting material can generate magnetic traps with significantly reduced noise. Recently, several designs for superconducting chips have been theoretically analyzed and experimentally tested, for cases with many vortices considered as an average vortex density. Here we show theoretically, for the first time, how the magnetic field of a $\it single$ vortex, pinned by a superconducting nano-disc of radius $\sim$100 nm and combined with an external bias field parallel to the disc surface, yields a closed 3D trap for cold atoms. The size of the trap, and its height above the superconductor surface, are typically tens or hundreds of nanometers. We estimate the average lifetime $\tau$ of $^{87}$Rb (rubidium) atoms (subject to thermal escape and Majorana spin flips) in the range 0.05-1.0 ms. Next, we model the trap in a quantum adiabatic approximation and apply Fermi's rule to estimate the lifetime of $^{87}$Rb atoms in the ground state of this trap. We obtain similar lifetimes $\tau$ as in the semiclassical estimate, in the range 0.05-3.5 ms. We find that $\tau$ depends on the gradient $B_0$ of the vortex's magnetic field according to $\tau \sim(B_0)^{-2/3}$.

Fluctuations of the Bose–Einstein condensate

This paper gives a rigorous analysis of the fluctuations of the Bose–Einstein condensate for a system of non-interacting bosons in an arbitrary potential, assuming that the system is governed by the canonical ensemble. As a result of the analysis, we are able to tell the order of fluctuations of the condensate fraction as well as its limiting distribution upon proper centering and scaling. This yields interesting results. For example, for a system of n bosons in a 3D harmonic trap near the transition temperature, the order of fluctuations of the condensate fraction is n−1/2 and the limiting distribution is normal, whereas for the 3D uniform Bose gas, the order of fluctuations is n−1/3 and the limiting distribution is an explicit non-normal distribution. For a 2D harmonic trap, the order of fluctuations is n−1/2(log n)1/2, which is larger than n−1/2 but the limiting distribution is still normal. All of these results come as easy consequences of a general theorem.

Buffer-gas-cooled ion clouds in a classical Paul trap: superimposed stability diagrams and trapping capacity investigations

Ion clouds of different species and variable size are stored in a 3D Paul trap and detected after extraction from the trap. We report on measurements of the superimposed stability regions of four simultaneously stored ion species. We determine the operating conditions for trapping capacity under variation of buffer gas pressure and observe space charge shifts for a specific ion in the presence of other elements.

Subwavelength optical trapping with a fiber-based surface plasmonic lens

We demonstrate three-dimensional (3D) optical trapping of subwavelength polystyrene beads and bacteria with a surface plasmonic lens fabricated on the endface of an optical fiber. To the best of our knowledge, this is the first demonstration of 3D trapping of subwavelength particles with single fiber optical tweezers. The optical power for achieving a stable 3D trap is smaller compared with conventional optical tweezers, indicating a stronger trap. Compared with surface plasmon tweezers, the trap enabled by our fiber tweezers is located ≈6 wavelengths away from the fiber endface, reducing thermal effects due to the metal absorption and preventing physical contact with the trapped objects.

Thermodynamic Properties of Ultracold Bose Gas: Transition Exponents and Universality

We report exact numerical calculation of chemical potential, condensate fraction and specific heat of $N$ non-interacting bosons confined in an isotropic harmonic oscillator trap in one, two and three dimensions, as also for interacting bosons in a 3D trap. Quasi phase transitions are observed in all these cases, including one-dimension, as shown by a rapid change of all the thermodynamic quantities at the transition point. The change becomes more rapid as $N$ increases in 2D and 3D cases. However with increase in $N$, the sudden change in the nature of specific heat, gets gradually wiped out in 1D, while it becomes more drastic in 2D and 3D. The sudden change in the nature of condensate fraction and chemical potential as $N$ increases becomes more drastic even in 1D. Defining transition exponents, which characterize the nature of a thermodynamic quantity at the transition point of a quasi phase transition, we evaluate them by careful numerical calculation very near the transition temperature. These exponents are found to be independent of the size of the system and whether the bosons are interacting or not, demonstrating their universality property.

Cooling molecules the optoelectric way

In a newly implemented technique, the complex rotational and vibrational motions of molecules are not a hindrance but a help.

How to write a paper for Rapid Communications in Mass Spectrometry

How to write a paper for <i>Rapid Communications in Mass Spectrometry</i>

Transport of charged particles by adjusting rf voltage amplitudes

We propose a planar architecture for scalable quantum information processing (QIP) that includes X-junctions through which particles can move without micromotion. This is achieved by adjusting radio frequency (rf) amplitudes to move an rf null along the legs of the junction. We provide a proof-of-principle by transporting dust particles in three dimensions via adjustable rf potentials in a 3D trap. For the proposed planar architecture, we use regularization techniques to obtain amplitude settings that guarantee smooth transport through the X-junction.

Infrared spectroscopy of ionized corannulene in the gas phase

The gas-phase infrared spectra of radical cationic and protonated corannulene were recorded by infrared multiple-photon dissociation (IRMPD) spectroscopy using the IR free electron laser for infrared experiments. Electrospray ionization was used to generate protonated corannulene and an IRMPD spectrum was recorded in a Fourier-transform ion cyclotron resonance mass spectrometer monitoring H-loss as a function of IR frequency. The radical cation was produced by 193-nm UV photoionization of the vapor of corannulene in a 3D quadrupole trap and IR irradiation produces H, H(2), and C(2)H(x) losses. Summing the spectral response of the three fragmentation channels yields the IRMPD spectrum of the radical cation. The spectra were analyzed with the aid of quantum-chemical calculations carried out at various levels of theory. The good agreement of theoretical and experimental spectra for protonated corannulene indicates that protonation occurs on one of the peripheral C-atoms, forming an sp(3) hybridized carbon. The spectrum of the radical cation was examined taking into account distortions of the C(5v) geometry induced by the Jahn-Teller effect as a consequence of the degenerate (2)E(1) ground electronic state. As indicated by the calculations, the five equivalent C(s) minima are separated by marginal barriers, giving rise to a dynamically distorted system. Although in general the character of the various computed vibrational bands appears to be in order, only a qualitative match to the experimental spectrum is found. Along with a general redshift of the calculated frequencies, the IR intensities of modes in the 1000-1250 cm(-1) region show the largest discrepancy with the harmonic predictions. In addition to CH "in-plane" bending vibrations, these modes also exhibit substantial deformation of the pentagonal inner ring, which may relate directly to the vibronic interaction in the radical cation.

DC potentials applied to an end-cap electrode of a 3D ion trap for enhanced MS n functionality

The effects of the application of various DC magnitudes and polarities to an end-cap of a 3D quadrupole ion trap throughout a mass spectrometry experiment were investigated. Application of a monopolar DC field was achieved by applying a DC potential to the exit end-cap electrode, while maintaining the entrance end-cap electrode at ground potential. Control over the monopolar DC magnitude and polarity during time periods associated with ion accumulation, mass analysis, ion isolation, ion/ion reaction, and ion activation can have various desirable effects. Included amongst these are increased ion capture efficiency, increased ion ejection efficiency during mass analysis, effective isolation of ions using lower AC resonance ejection amplitudes, improved temporal control of the overlap of oppositely charged ion populations, and the performance of “broad-band” collision induced dissociation (CID). These results suggest general means to improve the performance of the 3D ion trap in a variety of mass spectrometry and tandem mass spectrometry experiments.

Rapid separation, identification, and quantification of coumarins in Peucedanum ostruthium by high-performance liquid chromatography with diode-array detection and mass spectrometry

The genus Peucedanum (Apiaceae) contains over 120 species. Various coumarins are typical for its family and, therefore, can be used to distinguish between closely related species [1]. As the rhizomes of Peucedanum ostruthium are traditionally used in the alpine region as herbal drug and as ingredient of liqueurs and bitters [2], there is a need for quality control of this drug (“Radix Imperatoriae“). A high performance liquid chromatography-diode array detector-mass spectrometry (HPLC-DAD-MS) method has been developed for the simultaneous separation and identification of the six main coumarins, Oxypeucedanin-hydrate, Oxypeucedanin, Ostruthol, Imperatorin, Isoimperatorin, and Ostruthin, in the dichloromethane extract of the dried rhizomes of Peucedanum ostruthium. Fast HPLC separation of the (furano)coumarins could be achieved on a Aquasil C18 column (150×2,1, particle size: 3µm) using a mobile phase gradient of acetonitrile-water modified with 0,01% acetic acid. Peak assignment and purity control were obtained by multistage LC-MS using a 3D quadrupole ion trap instrument equipped with an orthogonal electrospray ionisation source. The identity of the main compounds was confirmed either by comparison with reference compounds (Oxypeucedanin, Imperatorin and Isoimperatorin), or by isolation (Oxypeucedaninhydrate, Ostruthol and Ostruthin) and structural characterization by NMR and MS. Moreover, the content of the main coumarins was quantified in various batches of commercial and field-collected rhizomes of Peucedanum ostruthium by this newly established HPLC-DAD method. Hence, it can be used for performing a fast profiling and quantification of the main coumarins in samples of “Radix Imperatoriae“.

Spectrum of Two-Level Systems with Discrete Frequency Fluctuations

We study, theoretically and experimentally, an ensemble of two-level systems coupled to an environment which induces random jumps in their resonant frequency. We present a closed-form formula for the spectrum in terms of the resonant frequency distribution and the Poisson rate constant. For a normal distribution the spectrum deviates from a generalized Gumbel function, a well-known result for continuous stochastic Gaussian processes. We perform experiments with optically trapped cold 87Rb atoms and show that the predictions of our theory for a 3D harmonic trap match the measured spectra without fitting parameters.

Meissner transport current in flat films of arbitrary shape and a magnetic trap for coldatoms

The use of superconducting films in the Meissner state reduces the level of noise inmicro- and nanochips. Here we present a numerical scheme for computing the Meissnertransport current distribution in superconducting films of arbitrary shape, includingmultiply connected films. The scheme is used for simulating a 3D magnetic trap for coldatoms. Our algorithm is easily generalized for computing the Meissner–London distributionof transport current.

Multiple traps created with an inclined dual-fiber system

Multiple optical traps allow one to manipulate multiple particles simultaneously, to characterize interactions in colloidal systems, and to assemble particles into complex structures. Most of the current multiple optical traps are realized with microscope objective-based optical tweezers, which are bulky in size. In this article, we created multiple optical traps with an inclined dual-fiber optical tweezers setup. One 3D trap and two 2D traps were formed at different vertical levels with adjustable separations and positions. We demonstrated that this fiber-based trapping system can be used as a simple block to perform multiple functions, such as particle grouping, separation, and stacking. Moreover, we found that multiple beads can be trapped and stacked up in three dimensions. Compared with those formed with objective-based optical tweezers, the multiple traps presented here are small in size and independent of the objective or the substrate, and hence hold the promise to be integrated in microfluidic systems. This fiber-based multiple traps can be used for on-chip parallel manipulation, particle separation, and characterization of interactions of colloidal and biological systems.

Computer Simulation of the Gap-Tripole Ion Trap with Linear Injection, 3D Ion Accumulation, and Versatile Packet Ejection

The behavior of a completely new ion trap is shown with SIMION 7.0 simulations. The simulated trap, which was a mix of a linear and a 3D trap, was made by axially setting two ion guides with a gap between them. Each guide consisted of three rods with three symmetrically delayed radio frequency (rf) voltages (tripole). The "injected" ions were linearly contained by pulsed potentials on the entrance and exit plates. Then the three-dimensional (3D) rf field in the gap, which was created by the tripole special rod arrangement, could trap the ions when the translational energy was dampened by collisions with low-pressure nitrogen. Because the injected ions were trapped in the small gap, the trapping cycle could be repeated many times before ion ejection, so a high concentrated ion cloud could be obtained. This trapping and accumulation methodology is not possible in most conventional multipole linear traps with even number of poles. Compared with quadrupole linear trap at the same rf amplitude, tripole lost more ions due to strong charge repulsion in the ion cloud. However, tripole could catch up the ions at higher voltage. Radial and axial mass-independent ejection of the ions localized in the tripole gap was very simple, compared with conventional linear ion traps that need extra and complicated electrodes for effective axial ejection.

Observation of sub-Doppler temperatures in bosonic magnesium

Temperatures below the Doppler limit of $1.9\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$ have been observed in magnesium. The strong cooling transition was modified by a coherent two-color excitation exploiting the longer lifetime of an upper level. We developed a theoretical model to describe the light forces and cooling originating from the induced quantum interference in a three-level system. Time-of-flight measurements verified temperatures of $500\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ in a one-dimensional (1D) molasses in accordance with our theoretical model. By implementing this scheme in a 3D magneto-optical trap with a single ir beam, temperatures as low as $1\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$ could be realized. For ideal conditions we extrapolate to temperatures of $50\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$. With cooling times of about $1\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$, a fast and efficient cooling scheme was realized, particularly attractive for optical frequency standards.

Inductively coupled plasma mass spectrometry, coincidence laser spectroscopy (ICP-MS-CLS), simulation of the transmission efficiency of a 3D quadrupole ion trap for cooling energetic ions from the ICP prior to optical detection

A fundamental requirement of ICP-MS-CLS is a post mass separation ion beam with an energy spread of less than ∼0.2 eV to enable efficient pumping of fluorescent lines with a narrow band (Δν ∼ 100 kHz) laser for the optical detection step. The role of a 3D quadrupole ion trap for ion beam cooling, as an accessory for a new generation of ICP-MS-CLS (inductively coupled plasma mass spectrometry, coincidence laser spectroscopy) (B. L. Sharp, P. S. Goodall, L. M. Ignjatovic and H. Teng, J. Anal. At. Spectrom., 2007, 22, 1447) instrument, was investigated by means of numerical simulation. Whereas in-trap ion cooling is well established, it was found that extraction of cooled ions from the trap introduced additional broadening and a loss of transmission efficiency. Modelling was based on a beam of 20 eV mean energy with a spread of 3 eV which represents a worst case scenario for the ions derived from an ICP source. The efficiency of the cooling process (trapping + extraction), as well as the energy distributions of ions exiting the trap, were calculated and compared for several methods of extraction. Trapping efficiencies of ∼25% were obtained at buffer gas pressures up to 10 mTorr. The addition of virtual reflectrons to the trap resulted in an improvement in the energy distribution of the trapped ions by lowering the wings of the distribution, but did not significantly improve the efficiency. Zero field, rf field only, quadrupolar field and homogeneous field ion extraction were investigated to recover ions from the trap, and of these quadrupolar extraction was best. However, extraction efficiency and ion energy distribution were inversely related so that quadrupolar extraction at Uq = 10 V yielded an exit ion energy distribution of 0.5 eV half width, compared with a trapped width of 0.03 eV, but with only 10% transmission efficiency. Thus, it was demonstrated that a 3D trap can be used to cool energetic ions for post-trap mass or spectroscopic examination, but the low efficiency makes it unsuitable for use with ICP-MS-CLS.