Ion Trap Research Articles

Charge exchange of slow highly charged ions from an electron beam ion trap with surfaces and 2D materials

Abstract Electron beam ion traps allow studies of slow highly charged ion transmission through freestanding 2D materials as an universal testbed for surface science under extreme conditions. Here we review recent studies on charge exchange of highly charged ions in 2D materials. Since the interaction time with these atomically thin materials is limited to only a few femtoseconds, an indirect timing information will be gained. We will therefore discuss the interaction separated in three participating time regimes: energy deposition (charge exchange), energy release (secondary particle emission), and energy retention (material modification).

Discrimination of subtypes of sesquiterpene pyridine alkaloids using a multistage ion fragmentation strategy

Sesquiterpene pyridine alkaloids (SPAs) are a large group of macrocyclic dilactones formed by dihydro-β-agarofuran sesquiterpenes and pyridine dicarboxylic acids, which have aroused widespread interest in the field of medicine due to their significant biological activities. In order to achieve accurate and rapid characterization of SPAs, previous studies have systematically investigated their fragmentation patterns in MS2, but there are still some problems that need to be resolved, such as distinction between wilfordate (W)- and evoninate (E)-subtypes, as well as determination of the substituent position. In this paper, a comparative analysis of W- and E-subtypes of SPAs was carried out by a product ion scanning-multistage fragmentation (PIS-MSn) strategy using ultra-high-performance liquid chromatography/linear ion trap quadrupole/orbitrap mass spectrometry (UHPLC/LTQ-Orbitrap-MS). The precursor ions for MSn were selected from the ions related with pyridine dicarboxylic acid moiety in MS2 spectrum, such as the ions at m/z 206, 178, and 160. The results showed that the product ions at m/z 104 or 117 were produced in the MS4 spectra of W-subtype SPAs ([M+H]+ > m/z 160 > m/z 132 > m/z 104 or 117). The ion at m/z 104 was produced when acetyloxyl group was present at C-5, whereas the ion at m/z 117 was produced when hydeoxyl group was present at C-5. Neither of the above characteristic ions were produced in the MS4 spectra of E-subtype SPAs. The fragmentation mechanism was also deduced. In addition, 13 SPAs were identified from the root of Tripterygium wilfordii, including 1 unknown compound using the MS/MS fragmentation pattern. The findings in this study enable the differentiation between W- and E-subtypes of SPAs and, to a certain extent, solve the problem of substituent position, which is of great significance for the accurate and in-depth identification of SPAs.

Sodium iodide symporter immunolabelling as a predictor of clinical iodide uptake in canine thyroid carcinoma: A preliminary study.

Thyroid follicular tumours may take up iodide via the sodium-iodide symporter. Knowledge of iodide uptake could then allow treatment with I-131 in dogs with high-risk tumours. The objective of this study was to determine the relationship between clinically detectable iodide uptake (as determined by scintigraphy and/or thyroxine concentrations) and sodium iodide symporter immunohistochemical labelling on histologically fixed thyroid tumours. Nineteen dogs were identified who were diagnosed with thyroid carcinoma and underwent surgery from November 2017 to July 2021. All had recorded thyroid hormone concentrations and were hyperthyroid and/or underwent preoperative nuclear imaging using planar scintigraphy (technetium-99m or I-123), or I-124 PET-CT. All dogs subsequently underwent surgery to remove the thyroid mass. Twenty-two tumours were submitted for histopathologic analysis immediately following surgery, which confirmed a diagnosis of thyroid carcinoma for each tumour. Images and/or thyroid hormone concentrations were reviewed for the included cases, and tumours were sorted into an avid/functional group (group 1) and a non-avid/functional group (group 2). The tumour tissues were re-examined histologically using sodium iodide symporter (NIS) immunohistochemistry (IHC). Group 1 contained 15 avid/functional tumours. Twelve of these tumours had membranous NIS IHC labelling. Group 2 contained 7 non-avid tumours. One of these tumours had membranous NIS IHC labelling. This resulted in an overall sensitivity and specificity for identification of avid/functional tumours with membranous NIS of 80.0% and 85.7%, respectively. NIS IHC may predict ion trapping in canine follicular thyroid tumours. Further studies using iodide-based imaging are warranted to better determine the clinical utility of this diagnostic modality.

Ion Spectroscopy Reveals Structural Difference for Proteins Microhydrated by Retention and Condensation of Water.

Protein ubiquitin in its +7 charge state microhydrated by 5 and 10 water molecules has been interrogated in the gas phase by cold ion UV/IR spectroscopy. The complexes were formed either by condensing water onto the unfolded bare proteins in a temperature-controlled ion trap or by incomplete dehydration of the folded proteins. In the case of cryogenic condensation, the UV spectra of the complexes exhibit a resolved vibrational structure, which looks similar to the spectrum of bare unfolded ubiquitin. The spectra become, however, broad-band with no structure when complexes of the same size are produced by incomplete dehydration under soft conditions of electrospray ionization. We attribute this spectroscopic dissimilarity to the structural difference of the protein: condensing a few water molecules cannot refold the gas-phase structure of the bare ubiquitin, while the retained water preserves its solution-like folded motif through evaporative cooling. This assessment is firmly confirmed by IR spectroscopy, which reveals the presence of free NH and carboxylic OH stretching vibrations only in the complexes with condensed water.

Experimental Proposal on Non-Hermitian Skin Effect by Two-dimensional Quantum Walk with a Single Trapped Ion

Non-Hermitian Hamiltonians are widely used in describing open systems with gain and loss, among which a key phenomenon is the non-Hermitian skin effect. Here we report an experimental scheme to realize a two-dimensional (2D) discrete-time quantum walk with non-Hermitian skin effect in a single trapped ion. It is shown that the coin and 2D walker states can be labeled in the spin of the ion and the coherent-state lattice of the ion motion, respectively. We numerically observe a directional bulk flow, whose orientations are controlled by dissipative parameters, showing the emergence of the non-Hermitian skin effect. We then discuss an experimental implementation of our scheme in a laser-controlled trapped Ca+ ion. Our experimental proposal may be applicable to research of dissipative quantum walk systems and may be able to generalize to other platforms, such as superconducting circuits and atoms in cavity.

Capturing ion trapping and detrapping dynamics in electrochromic thin films

Ion trapping has been found to be responsible for the performance degradation in electrochromic oxide thin films, and a detrapping procedure was proved to be effective to rejuvenate the degraded films. Despite of the studies on ion trapping and detrapping, its dynamics remain largely unknown. Moreover, coloration mechanisms of electrochromic oxides are also far from clear, limiting the development of superior devices. Here, we visualize ion trapping and detrapping dynamics in a model electrochromic material, amorphous WO3. Specifically, formation of orthorhombic Li2WO4 during long-term cycling accounts for the origin of shallow traps. Deep traps are multiple-step-determined, composed of mixed W4+-Li2WO4, amorphous Li2WO4 and W4+-Li2O. The non-decomposable W4+-Li2WO4 couple is the origin of the irreversible traps. Furthermore, we demonstrate that, besides the typical small polaron hopping between W5+ ↔ W6+ sites, bipolaron hopping between W4+ ↔ W6+ sites gives rise to optical absorption in the short-wavelength region. Overall, we provide a general picture of electrochromism based on polaron hopping. Ion trapping and detrapping were demonstrated to also prevail in other cathodic electrochromic oxides. This work not only provides the ion trapping and detrapping dynamics of WO3, but also open avenues to study other cathodic electrochromic oxides and develop superior electrochromic devices with great durability.

Mimicking Bidirectional Inhibitory Synapse Using a Porous-Confined Ionic Memristor with Electrolyte/Tris(4-aminophenyl)amine Neurotransmitter.

Ionic memristors can emulate brain-like functions of biological synapses for neuromorphic technologies. Apart from the widely studied excitatory-excitatory and excitatory-inhibitory synapses, reports on memristors with the inhibitory-inhibitory synaptic behaviors remain a challenge. Here, the first biaxially inhibited artificial synapse is demonstrated, consisting of a solid electrolyte and conjugated microporous polymers bilayer as neurotransmitter, with the former serving as an ion reservoir and the latter acting as a confined transport. Due to the migration, trapping, and de-trapping of ions within the nanoslits, the device poses inhibitory synaptic plasticity under both positive and negative stimuli. Remarkably, the artificial synapse is able to maintain a low level of stable nonvolatile memory over a long period of time (≈60min) after multiple stimuli, with feature-inferencing/-training capabilities of neural node in neuromorphic computing. This work paves a reliable strategy for constructing nanochannel ionic memristive materials toward fully inhibitory synaptic devices.

Penning micro-trap for quantum computing.

Trapped ions in radio-frequency traps are among the leading approaches for realizing quantum computers, because of high-fidelity quantum gates and long coherence times1-3. However, the use of radio-frequencies presents several challenges to scaling, including requiring compatibility of chips with high voltages4, managing power dissipation5 and restricting transport and placement of ions6. Here we realize a micro-fabricated Penning ion trap that removes these restrictions by replacing the radio-frequency field with a 3T magnetic field. We demonstrate full quantum control of an ion in this setting, as well as the ability to transport the ion arbitrarily in the trapping plane above the chip. This unique feature of the Penning micro-trap approach opens up a modification of the quantum charge-coupled device architecture with improved connectivity and flexibility, facilitating the realization of large-scale trapped-ion quantum computing, quantum simulation and quantum sensing.

Experimental verification of quantum contextuality using a weak measurement in a single trapped ion

Experimental verification of quantum contextuality using a weak measurement in a single trapped ion

Plasma metabolomics identifies S-adenosylmethionine as a biomarker and potential therapeutic target for vascular aging in older adult males

Brachial-ankle pulse wave velocity (baPWV) is a noninvasive index of vascular aging. However, the metabolic profile underlying vascular aging has not yet been fully elucidated. The current study aimed to identify circulating markers of vascular aging as assessed by baPWV and to elucidate its mechanism from a metabolomic perspective in older adults. A total of 60 and 61 Chinese male participants aged ≥80 years were recruited to the metabolome and validation cohorts, respectively. The baPWV of participants was measured using an automatic waveform analyzer. Plasma metabolic profile was investigated using ultra-performance liquid chromatography coupled with triple quadrupole linear ion trap tandem mass spectrometry. Orthogonal partial least squares (OPLS) regression modeling established the association between metabolic profile and baPWV to determine important metabolites predictive of vascular aging. Additionally, an enzyme-linked immunosorbent assay was employed to validate the metabolites in plasma and culture media of vascular smooth muscle cells in vitro. OPLS modeling identified 14 and 22 metabolites inversely and positively associated with baPWV, respectively. These 36 biomarkers were significantly enriched in seven metabolite sets, especially in cysteine and methionine metabolism (p <0.05). Notably, among metabolites involved in cysteine and methionine metabolism, S-adenosylmethionine (SAM) level was inversely related to baPWV, with a significant correlation coefficient in the OPLS model (p <0.05). Furthermore, the relationship between SAM and vascular aging was reconfirmed in an independent cohort and at the cellular level in vitro. SAM was independently associated with baPWV after adjustments for clinical covariates (β = −0.448, p <0.001) in the validation cohort. In summary, plasma metabolomics identified an inverse correlation between SAM and baPWV in older males. SAM has the potential to be a novel biomarker and therapeutic target for vascular aging.

Fragmentation of water clusters formed in helium nanodroplets by charge transfer and Penning ionization.

Helium nanodroplets ("HNDs") are widely used for forming tailor-made clusters and molecular complexes in a cold, transparent, and weakly interacting matrix. The characterization of embedded species by mass spectrometry is often complicated by the fragmentation and trapping of ions in the HNDs. Here, we systematically study fragment ion mass spectra of HND-aggregated water and oxygen clusters following their ionization by charge transfer ionization ("CTI") and Penning ionization ("PEI"). While the efficiency of PEI of embedded clusters is lower than for CTI by about factor 10, both the mean sizes of detected water clusters and the relative yields of unprotonated cluster ions are significantly larger, making PEI a "soft ionization" scheme. However, the tendency of ions to remain bound to HNDs leads to a reduced detection efficiency for large HNDs containing >104 helium atoms. These results are instrumental in determining optimal conditions for mass spectrometry and photoionization spectroscopy of molecular complexes and clusters aggregated in HNDs.

The Magnesium Dication and Water Synergistically Promote the Protonolysis of Two of the B-C Bonds in the Tetraphenylborate Anion.

Analytes are sampled from both solution phase and gas-phase environments during the ESI process, and thus, the mass spectrum that is measured can reflect both solution and gas-phase conditions. In the gas-phase regime, ion-molecule reactions can influence the types of ions that are observed. Herein, the synergistic effects of a Lewis acid (Mg2+) and background water are shown to lead to protonolysis of two of the B-C bonds of the tetraphenylborate ion in the gas phase, giving rise to different ions at different reaction times in ESI-MS/MS experiments in a linear ion trap mass spectrometer. At short reaction times (1 ms), the expected adduct [Mg(BPh4)]+ is observed. At 10 ms, [(HO)Mg(BPh3)]+ and [(HO)2Mg(BPh2)]+ are observed. At 100 ms, the water adducts [(HO)2Mg(BPh2)(H2O)]+ and [(HO)2Mg(BPh2)(H2O)2]+ appear, and these become the dominant ions at longer reaction times. DFT calculations provide a plausible explanation as to why only [(HO)Mg(BPh3)]+ and [(HO)2Mg(BPh2)]+ but not [(HO)3Mg(BPh)]+ are observed.

Laser-type cooling with unfiltered sunlight.

Cooling of systems to sub-Kelvin temperatures is usually done using either a cold bath of particles or spontaneous photon scattering from a laser field; in either case, cooling is driven by interaction with a well-ordered cold (i.e., low-entropy) system. However, there have recently been several schemes proposed for "cooling by heating," in which raising the temperature of some mode drives the cooling of the desired system faster. We discuss how to cool a trapped ion to its motional ground state using unfiltered sunlight at 5800K to drive the cooling. We show how to treat the statistics of thermal light in a single-mode fiber for delivery to the ion and show experimentally how the blackbody spectrum is strongly modified by being embedded in quasi-one-dimension. Quantitative estimates for the achievable cooling rate with our measured fiber-coupled low-dimensional sunlight show promise for demonstrating this implementation of cooling by heating.

L-Mn dielectronic recombination of cerium ions in a room-temperature EBIT

We explore the dielectronic recombination structures at the electron beam ion trap at Jagiellonian University in Cracow, emited by cerium that is produced by the high-current cathode made of iridium and cerium. Small amounts of these elements evaporate from the cathode and form low-intensity admixtures within the electron-ion plasma in the EBIT. Their presence and specific ionic population can be observed by examining the spectral characteristics resulting from the DR process. Results have been compared with flexible atomic code calculations, working in unresolved transition array mode, providing identification of the charge states. Here we show that this mode provides quick calculations of very complex data with enough reliability for experimental comparison. These observations highlight which DR features and corresponding charge states that should be present in spectra obtained in EBITs with similar cathode specifications.

Ion trap with in-vacuum high numerical aperture imaging for a dual-species modular quantum computer.

Photonic interconnects between quantum systems will play a central role in both scalable quantum computing and quantum networking. Entanglement of remote qubits via photons has been demonstrated in many platforms; however, improving the rate of entanglement generation will be instrumental for integrating photonic links into modular quantum computers. We present an ion trap system that has the highest reported free-space photon collection efficiency for quantum networking. We use a pair of in-vacuum aspheric lenses, each with a numerical aperture of 0.8, to couple 10(1)% of the 493nm photons emitted from a 138Ba+ ion into single-mode fibers. We also demonstrate that proximal effects of the lenses on the ion position and motion can be mitigated.

Liquid chromatography-mass spectrometry-based strategy for systematic profiling of chemical components and associated quantitative analysis of quality markers in Qi-Wei-Tong-Bi oral liquid.

Qi-Wei-Tong-Bi oral liquid (QWTB), a famous Chinese medicine preparation composed of seven crude drugs has a good therapeutic effect on rheumatoid arthritis and is widely used in China.However, its chemical composition and quality control have not been comprehensively and systematically investigated. In this study, high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was employed for its chemical profiling. As a result, 100 components were chemically characterized. Additionally, high-performance liquid chromatography coupled with a quadrupole linear ion trap mass spectrometry method was developed to simultaneously quantify nine bioactive components (hyperoside, ononin, quercetin, sinomenine, magnoflorine, gallic acid, protocatechuic acid, monotropein, and cyclo-(Pro-Tyr)) in multiple-reaction monitoring mode. After successful validation in terms of linearity, precision, repeatability, and recovery, the assay method was applied for the determination of 10 batches of QWTB. The results showed that QWTB was enriched in sinomenine and magnoflorine with the highest amount up to hundreds or even thousands of µg/mL, while quercetin, ononin, cyclo-(Pro-Tyr), and hyperoside were much lower with the lowest content below 10µg/mL. This study work would help to reveal the chemical profiling and provide a valuable and reliable approach for quality evaluation and even pharmacodynamic material basis studies of QWTB.

Electron collisional excitation cross-section measurements and modeling for select Ni-like to Ge-like gold transitions

We have experimentally determined the electron collisional excitation cross-sections for several 3d→4f and 3d→5f excitations in Ni- to Ge-like Au at energies of ∼ 0.4, 1, 2, and 3 keV above threshold energy, ET, for the 3d→4f excitations ( ET ∼ 2.5 keV) and ∼ 0.2, 1, and 2 keV above threshold energy for the 3d→5f excitations ( ET ∼ 3.3 keV). The cross-section measurements are possible by using the GSFC micro-calorimeter to record emission spectra from beam plasmas created in the Livermore EBIT-I electron beam ion trap. The cross-sections are experimentally determined from the ratio of the measured intensities of the collisionally excited lines to the intensities of the radiative recombination lines in monoenergetic electron distribution EBIT-I plasmas. The effects of polarization and Auger processes in the beam plasmas are accounted for in the cross-section determination. Experimentally determined cross-sections are compared with those from HULLAC, DWS, and FAC calculations. The measurements exhibit significant differences with the calculations of these excitation cross-sections.

Exact simulation of classical heat engine cycles using single-ion phonon laser

Heat engines are essential devices in modern industry, converting heat energy into useful mechanical work via their working substances. Here we experimentally simulate the conventional heat engine by employing the vibrational mode of a single trapped ion as the working substance. In contrast to simply employing the ion in thermal motion, we consider coherently stimulating the ion’s vibrational motion as the phonon laser, which helps acquire clearer results by effectively suppressing the thermal fluctuation. As such, we demonstrate in an exact and high signal-to-noise way the standard steps of both the Otto and Carnot cycles in a single ion, and compare their maximum efficiencies by monitoring the amplitude and frequency of the vibration. Our work witnesses an interesting single-atom thermal engine using coherently controlled phonons. It would be the smallest platform for simulating or demonstrating classical thermodynamic laws and phenomena at a single ion scale via optical manipulation techniques for phonon lasers.

Terminal Copper Nitrenoid Formation and Reactivity Induced by Absorption to an Antenna Ligand.

Copper nitrenoids are key intermediates in copper-catalyzed direct C-H amination reactions. Further development of this important reaction relies on knowing the properties and reactivity of the nitrenoid intermediates. This work utilizes antenna ligands to form copper nitrenoid complexes and monitor the consecutive C-H amination reactions under well-defined single-molecule conditions in the gas phase. The [Cu(Lphoto)(Lazide)]+ precursors (Lphoto is a bidentate antenna ligand, and Lazide is an organic azide) were stored in an ion trap at 3.5 K and irradiated by visible light, which resulted in denitrogenation of the complex. Further irradiation of the copper nitrenoid led to the consecutive C-H amination of the antenna ligand. The nitrenoid complexes, as well as the products of the C-H amination, were characterized by helium tagging IRPD spectroscopy, and the mechanism was described by DFT calculations. This research demonstrates that the antenna ligands can be used to promote the denitrogenation of metal azides in the gas phase and also channel the internal energy to promote further reactivity, which opens a new way to study the reactivity of highly reactive species under well-defined conditions.

Terminal Copper Nitrenoid Formation and Reactivity Induced by Absorption to an Antenna Ligand

AbstractCopper nitrenoids are key intermediates in copper‐catalyzed direct C−H amination reactions. Further development of this important reaction relies on knowing the properties and reactivity of the nitrenoid intermediates. This work utilizes antenna ligands to form copper nitrenoid complexes and monitor the consecutive C−H amination reactions under well‐defined single‐molecule conditions in the gas phase. The [Cu(Lphoto)(Lazide)]+ precursors (Lphoto is a bidentate antenna ligand, and Lazide is an organic azide) were stored in an ion trap at 3.5 K and irradiated by visible light, which resulted in denitrogenation of the complex. Further irradiation of the copper nitrenoid led to the consecutive C−H amination of the antenna ligand. The nitrenoid complexes, as well as the products of the C−H amination, were characterized by helium tagging IRPD spectroscopy, and the mechanism was described by DFT calculations. This research demonstrates that the antenna ligands can be used to promote the denitrogenation of metal azides in the gas phase and also channel the internal energy to promote further reactivity, which opens a new way to study the reactivity of highly reactive species under well‐defined conditions.