Lifetime Of Ions Research Articles

Tuning the Photoluminescence Properties of β‐NaYF4:Yb,Er by Bi3+ Doping Strategy

AbstractThe low luminous efficiency of upconversion materials limits their practical applications in various fields. The present study focuses on the efficient upconversion enhancement of β‐NaYF4:Yb,Er induced by Bi3+ doping. The XRD and SEM results show that introducing Bi3+ into the matrix lattice changes the microstructure and particle size of the crystal. The photoluminescence spectra show that at 6% Bi3+ doping, the red and green emission intensities are enhanced by 12 and 8 times, respectively. The reason could be the lattice distortion caused by Bi3+ doping, breaking the partial forbidden transition of rare‐earth ions. The fluorescence lifetime measurement reveals that the Bi3+ doping changes the environment around erbium ions, affecting the energy level lifetime of erbium ions, explaining the luminescence dynamics law. The present study provides a facile route to achieve nano/microstructures with intense upconversion luminescence with potential applications in optoelectronic devices.

Ion fluxes and memory effects in an Ar–O2 modulated radiofrequency-driven atmospheric pressure plasma jet

In this work we used molecular beam mass spectrometry to characterize ion fluxes produced by a modulated radiofrequency (RF)-driven atmospheric pressure plasma jet operating in a homogeneous gas environment (Ar + 1% O2). The influence of the RF modulation frequency (100 Hz to 20 kHz) on the ion fluxes was investigated by time-resolved measurements, and the lifetimes of the dominant ions, O2 +, NO+, O−, O2 − and O3 −, were found to be 28 ± 2, 117 ± 8, 7.3 ± 0.4, 17 ± 1 and 23 ± 2 μs, respectively. The absolute ion densities in the near afterglow region were found to be of the order of 1011 cm−3. Significant differences in the dynamics of the positive and negative ions were found; these are explained by the presence of electrons at similar densities in the afterglow produced by electron detachment reactions from negative ions due to the large concentrations of atomic oxygen and singlet delta oxygen. Transitions in ion flux dynamics for different modulation frequencies and at the startup of the plasma were analyzed together with intensified charge coupled device images recording the plasma propagation in order to assess the dynamics of plasma plume propagation and how it is impacted by ‘memory effects’. Quantitative measurements of the ion densities enabling these memory effects are reported. The results in this paper highlight the tremendous impact of memory effects on plasma propagation and the corresponding pre-ionization.

Методы спектроскопии диссоциативного захвата электронов и теории функционала плотности для моделирования биологической активности производных хиноксалина

The molecules of 2-methylquinoxalin and 2,3-dimethylquinoxalin were studied by mass spectrometry of negative ions of resonant capture of slow (0-15 eV) electrons. These compounds have antimicrobial, antifungal, bactericidal and preservative properties, and are widely used in medicine and the food industry. The average lifetime of molecular negative ions (NI)relative to electron auto-cleavage is measured experimentally. The most probable structures of fragment ions ([M – H]–, formed during the decay of molecular NI, are revealed. Within the framework of the Arrhenius approximation, the value of the adiabatic electron affinity (EAa) was estimated. It is found that the theoretical values of EAa calculated by the B3LYP/6-31+G(d) method with minimal addition of diffuse functions as the difference between the total energies of the neutral molecule and the radical anion correlate with the values of EAa obtained from the experiment.

Dynamic control of Purcell enhanced emission of erbium ions in nanoparticles

The interaction of single quantum emitters with an optical cavity enables the realization of efficient spin-photon interfaces, an essential resource for quantum networks. The dynamical control of the spontaneous emission rate of quantum emitters in cavities has important implications in quantum technologies, e.g., for shaping the emitted photons’ waveform or for driving coherently the optical transition while preventing photon emission. Here we demonstrate the dynamical control of the Purcell enhanced emission of a small ensemble of erbium ions doped into a nanoparticle. By embedding the nanoparticles into a fully tunable high finesse fiber based optical microcavity, we demonstrate a median Purcell factor of 15 for the ensemble of ions. We also show that we can dynamically control the Purcell enhanced emission by tuning the cavity on and out of resonance, by controlling its length with sub-nanometer precision on a time scale more than two orders of magnitude faster than the natural lifetime of the erbium ions. This capability opens prospects for the realization of efficient nanoscale quantum interfaces between solid-state spins and single telecom photons with controllable waveform, for non-destructive detection of photonic qubits, and for the realization of quantum gates between rare-earth ion qubits coupled to an optical cavity.

Investigation of Li Metal Plating and Dissolution on Graphite Electrodes

Li plating, meaning the deposition of metallic Lithium on the negative electrode is considered as one of the major degradation mechanisms in Li-Ion batteries. Therefore, understanding the processes which occur between metallic Lithium and state-of-the-art electrode materials, mainly Graphite, is important to improve the life-time of Li ion cells.Lithium plating and stripping is explored using an electrochemical model, which explicitly includes the growth of plated lithium as a competing process to the direct intercalation lithium ions [1]. The model is combined with a thermodynamically consistent transport theory and implemented in the simulation framework Battery and Electrochemistry Simulation Tool (BEST). The extended framework is used to conduct a first study regarding the impact of an inhomogeneous SEI growth on the deposition of metallic lithium.Moreover, we will present recent work on simulations of model experiments investigating the dissolution of lithium deposits on Graphite electrodes [2]. Different electrolyte formulations and configurations of a lithium metal disk on the electrode are investigated to evaluate different lithium transport pathways. In each experiment some pathways are intentionally blocked, thus yielding interesting insights into the dissolution mechanism. Post-mortem analysis on the Graphite electrodes is performed using Raman spectroscopy and glow-discharge optical emission spectroscopy (GD-OES) revealing the spatial distribution of the lithium at the end of the dissolution experiment. At the same time measurements of the open circuit voltage are performed to monitor the progress of the dissolution process. Our simulations are in very good qualitative agreement with measured OCV curves and the observed lithium distributions.Therefore, the simulations provide additional “in-operando” insights to the plating as well as the dissolution of a metallic lithium phase. With the mechanistic insights optimization of the electrode and cell architecture can be deduced which help to improve the life-time of Li ion cells.[1] S. Hein, T. Danner, and A. Latz, “An electrochemical model of lithium plating and stripping in lithium-ion batteries,” ACS Appl. Energy Mater., vol. 3, no. 9, p. acsaem.0c01155, Jul. 2020.[2] C. Hogrefe et al., “Mechanistic Details of the spontaneous Intercalation of Li Metal into Graphite Electrodes,” J. Electrochem. Soc., Nov. 2020.

Large‐Scale Fabrication of Surface Ion Traps on a 300 mm Glass Wafer

Herein, a large‐scale fabrication of radio frequency (RF) surface ion traps on a 300 mm glass wafer using a standard foundry process is reported. Established wafer‐level packaging process of electroplated Cu with Au finish is used to fabricate the surface electrodes directly on the glass wafer substrate. A trap is tested by loading it with laser‐cooled 88Sr+ ions. The trap shows a stable operation with RF amplitudes in the range of 100–250 V at 33 MHz frequency. The ion lifetime is on the order of 30 min with laser cooling with a vacuum chamber pressure of ≈5 × 10−11 mbar. These results demonstrate the potential of large‐size foundry glass substrates to realize scalable and integratable trapped ion‐based quantum devices.

Protein Analysis by Electrospray-Orbital Frequency Analyzer with Charge Detection Mass Spectrometry Algorithm.

Orbital frequency analyzer (OFA) is one of the electrostatic ion trap mass analysers for FTMS, which offers ultrahigh mass resolution and high ion charge capacity. In order to analyze multiply charged proteins and other large biological particles by means of charge detection mass spectrometry, a data processing algorithm was created to suit the image charge signal of nonharmonic waveform nature. The algorithm is capable of detecting collisions between ions and residual gas molecules, to determine lifetime of ions, and to evaluate the charge and mass values for ions having lifetime above a threshold. With the filtering of the lifetime and charge value, the chemical noise from small molecules and protein fragments can be eliminated in the reconstructed spectrum, facilitating measurement of protein content at a very low concentration, down to tens of nanomolars. The standard deviation of charge measurement is between 1.1 to 1.8 e for ions with oscillation lifetimes from 1 to 0.4 s, and this in turn determines the CDMS spectrum mass peak width. It has been found that the lower voltage setting of the OFA results in a larger population of ions surviving for longer times and thus produces narrower mass peak width. While OFA is able to run multiplexed CDMS without ion motion interference, coexisting ions of the same or very close m/z can cause interference between their image charge signals, which increases the error in charge determination.

Ring Current Decay During Geomagnetic Storm Recovery Phase: Comparison Between RBSP Observations and Theoretical Modeling

AbstractRing current decay during storm recovery phase may be affected by different loss processes. In this study, we have investigated the lifetimes of ring current ions (H+ and O+) of energies from 1 keV to several hundred keV at L shell from 3 to 6 during the storm recovery phase through a statistical survey. The observational data of 48 geomagnetic storms from March 2013 to May 2019 are collected based on Van Allen Probe observations. We find that (1) the observed lifetimes of H+ and O+ in general increase with L shell and (2) the lifetimes of H+ is short than that of O+ when E < ∼50 keV while the situation is reversed when E > ∼50 keV. In addition, we have made use of the charge exchange theory, combined with previous experimental results on the charge exchange cross section and two distribution models of neutral hydrogen atoms in the exosphere, so as to directly estimate the ring current ions decay caused by charge exchange mechanism only. Through the comparison between the model predictions of charge exchange lifetime and the observed lifetimes, we find that (3) the observed lifetimes are in general consistent with model results, which confirms that charge exchange is a dominant loss mechanism of ring current ions during storm recovery phase.

Determination of Electron Affinity on the Base of Experimentally Measured Lifetime of Negative Molecular Ions of Coumarin Derivatives

Resonance attachment of low-energy (0–15 eV) electrons to molecules of 4.7- and 6.7-dihydroxycoumarin was investigated by means of negative ion mass spectrometry. These natural compounds possess biological activity associated with antioxidant and bactericidal properties. The most probable structures of the fragment negative ions ([M – H]–, [M – 2H]–, [M – СО]–, [M – СОH]–, [M – СООH]– etc.) were predicted by means of analysis of decay channels for the molecular negative ions using the results of density functional theory calculations. Mean lifetime for molecular negative ions of 4.7-dihydroxycoumarin relative to electron autodetachment was measured. The adiabatic electron affinity (EAa) was estimated in the framework of the Arrhenius approximation. It was found that EAa values calculated at B3LYP/6-31+G(d) level with minimal addition of diffuse functions as a difference between the total energies of a neutral molecule and its radical anion correlate with experimental EAa values.

Ion Dynamics in an Atmospheric Source with Photoionization by Radiation of Laser Plasma

A pulsed source of ions with ionization of the substance under study at atmospheric pressure by the UV radiation of laser plasma is numerically simulated. The calculations are based on an original mathematical model that describes evolution of an ensemble of ions in the presence of superimposed gas-dynamic and electric fields with allowance for the Coulomb interaction. The model contains a system of the Navier–Stokes equations for gas-dynamic flows in the volume under study, the Poisson equation for the resulting distribution of electric field in such a volume, and the Lorentz equation for construction of ion trajectories from the ionization place to collecting diaphragm. Convergence of the relaxation method is demonstrated for the numerical solution of the main model equations. The dependence of ion current on applied voltage is studied. It is shown that the calculated results are in good agreement with the experimental data when finiteness of the ion lifetime due to recombination effect is taken into account.

A new technique for measurement of subrotational lifetime of molecular ions

Singly and multiply charged molecular ions are found in diverse environments and hold relevance for a wide range of research areas like combustion chemistry, accelerator physics, atmospheric sciences, plasma physics, astrophysics etc. Molecular dications are of special significance as they can be generated and studied comparatively easily in laboratory experiments. And they have enabled exploration of new and exciting phenomenon such as hydrogen migration, inter-atomic Coulombic decay, plasmonic excitations, orbital tomography etc. The lifetime of a molecular dication is one of its fundamental characteristics, whose measurement contributes to strengthening ab initio calculations and in predicting the concentration of its dissociation products. Most of the already reported lifetimes of molecular dications are in the range of nanoseconds to seconds and metastable states with lifetimes of the order of picoseconds have only been theoretical predicted and an experimental verification is pending. We present a method of measuring subrotational lifetimes of molecular dications formed in three-body sequential breakup of polyatomic molecular precursors. Specifically, we have measured the subrotational lifetime of hbox {SO}^{2+} , which is formed as an intermediate in the three-body sequential fragmentation of hbox {SO}_2^{3+}. The lifetime against dissociation is determined to be a fraction of the rotational period of hbox {SO}^{2+} and is of the order of few picoseconds. The method proposed is general and is not restricted to triatomic precursors.

An insight into the luminescent properties and Judd–Ofelt analysis of Eu3+ doped CaZn2(PO4)2 phosphors

A batch of Eu3+ doped CaZn2(PO4)2 orange–red emitting phosphors were synthesized by the conventional high temperature solid state reaction method. The structural, morphological and spectroscopic properties of the prepared samples were investigated by experimental and theoretical studies. Powder XRD and FTIR results were used to evaluate the structural aspects of the prepared phosphors and morphology was investigated by TEM analysis. The elemental composition analysis of the representative sample was made using energy dispersive x-ray spectroscopy (EDS). The optical properties were analyzed with the aid of UV–Vis-NIR spectroscopy and photoluminescence (PL) spectroscopy. The PL excitation spectra revealed that the prepared phosphors can be efficiently excited under 393 nm that matches well with the dominant emission band of near UV- LED chip. The PL emission studies demonstrate the emission of an orange–red light with CIE coordinates (0.6075, 0.3920) with color purity 100.0% under an excitation of 393 nm. The maximum emission intensity was observed at Eu3+ concentration of 4 mol%, from which the critical distance (Rc = 1.98 nm) of quenching was calculated. The emission spectra were further used to interpret the site symmetry of Eu3+ ions. Judd–Ofelt theory was employed to predict various radiative properties such as branching ratio (βr), total transition probability (AT), radiative life time (τcalc) and stimulated emission cross section (σe). The thermal stability of the prepared phosphor was investigated using temperature dependent luminescence spectra and the emission intensity was observed to remain at 70.83% of its initial value when the temperature is raised from 310 K to 430 K. The decay kinetics analysis confirms the lifetime of the activator ions to be in the millisecond (ms) range. The better stimulated emission cross section and strong orange–red emission suggest the Eu3+ doped CaZn2(PO4)2 system as a promising candidate in the design of various optoelectronic devices such as phosphor converted LEDs (pc- LEDs) and display panels.

Desorption processes in the measurement of weak currents

It was previously shown that the experimental measurement of the lifetime of gas-phase negative ions formed in autoionization states during resonant electron capture by molecules is inherently fraught with inaccuracy due to adsorption of ions on the walls of the ionization chamber, with some of them surviving there and staying stabilized as ‘eternal’ till they eventually desorb back into the vacuum and merge with the total ion flow; this leads to an upward distortion of lifetime measurements. This paper describes a technique for removing desorbed ions from the total flow using an ion filter that lets only gas-phase ions pass into the detection system but detains the desorbed ions due to the differences among their kinetic energies.

Mixing of States with the Same Symmetry in Negative Ions

An analysis is performed of the mass spectrum of resonance electron capture by tetracyanoquinodimethane molecules, in which long-lived negative molecular ions are detected. At 3.6 eV, the ions can be attributed to an electron-excited Feshbach resonance with an admixture of a long-lived ground state whose contribution to the superposition of two states yields a measurable ion lifetime in the microsecond range.

Incorporation of erbium ions into thin-film lithium niobate integrated photonics

As an active material with favorable linear and nonlinear optical properties, thin-film lithium niobate has demonstrated its potential in integrated photonics. Integration with rare-earth ions, which are promising candidates for quantum memories and transducers, will enrich the system with new applications in quantum information processing. Here, we investigate the optical properties at 1.5 μm wavelengths of rare-earth ions (Er3+) implanted in thin-film lithium niobate waveguides and micro-ring resonators. Optical quality factors near a million after post-annealing show that ion implantation damage can be repaired. The transition linewidth and fluorescence lifetime of erbium ions are characterized. The ion-cavity coupling is observed through a Purcell enhanced fluorescence from which a Purcell factor of 3.8 ± 0.5, compared with waveguide lifetime, is extracted. This platform is compatible with top-down lithography processes and leads to a scalable path for controlling spin-photon interfaces in photonic circuits.

Harmonic height distribution in pickup spectroscopy within electrostatic ion beam traps.

Pickup spectroscopy is a means of determining the abundance, mass, charge, and lifetime of ions oscillating in electrostatic ion beam traps. Here, we present a framework for describing the harmonic height distribution of the Fourier transform of the pickup signal and discuss the importance of the pickup positioning, bunch dynamics, and pickup width on the harmonic height distribution. We demonstrate the methodology using measurements from a newly constructed electrostatic ion beam trap.

Characterization of N-(2,6-dimethylphenyl)hydroxylamine adducts of 2′-deoxyguanosine under weakly basic conditions

Aromatic amines are a class of chemical carcinogens that are activated by cytochrome P450 enzymes to form arylhydroxylamines that are conjugated to form N-acetoxyarylamines or N-sulfonyloxyarylamines. These conjugates undergo N–O bond cleavage to become reactive nitrenium ions that may form DNA adducts. Numerous studies in the past using N-acetoxyarylamines to investigate DNA adduct formation were conducted, however, less is known in regard to DNA adduct formation directly from arylhydroxylamines - especially under conditions that mimic the physiological conditions of cells such as weakly basic conditions. In this study, 2′-deoxyguanosine (dG) was exposed to N-(2,6-dimethylphenyl)hydroxylamine (2,6-DMPHA) and N-phenylhydroxylamine (PHA) at pH 7.4 without enzymes and analyzed by liquid chromatography high resolution mass spectrometry (LC-HRMS). 2,6-DMPHA exposure resulted in the production of relatively low amounts of adducts however the identities of at least six different adducts that were formed through reactions with carbon, nitrogen and oxygen of 2′-deoxyguanosine were proposed based upon different analytical approaches including HRMS CID fragmentation and NMR analyses. Contrastively, PHA exposure under identical conditions resulted in one adduct at the C8 position. It was concluded from these results and results of theoretical calculations that nitrenium ions produced from 2,6-DMPHA were relatively more stable resulting in longer nitrenium ion lifetimes which ultimately led to greater potential for 2,6-DMPHA nitrenium ions to react with multiple sites on dG.

Динамика ионов в атмосферном источнике с фотоионизацией излучением лазерной плазмы

Представлены результаты математического моделирования импульсного источника ионов при атмосферном давлении с ионизацией анализируемого вещества УФ излучением лазерной плазмы. Расчеты проводились на основе разработанной авторами математической модели, описывающей эволюцию ансамбля ионов под действием скрещенных газодинамических и электрических полей с учетом эффектов кулоновского взаимодействия. Модель включает в себя систему уравнений Навье-Стокса для описания формирования газодинамических течений в исследуемом объеме, уравнение Пуассона для определения результирующего распределения электрического поля в этом объеме и уравнение Лоренца для построения ионных траекторий ионов от места их рождения до собирающей диафрагмы. Показана сходимость метода релаксации при численном решении основных уравнений модели. Исследована зависимость ионного тока от приложенного напряжения и показано, что учет конечности времени жизни ионов за счет эффекта рекомбинации позволяет получить хорошее согласие между расчетными и экспериментальными данными. Ключевые слова: лазерная плазма, математическое моделирование, ионный источник, газодинамические и электростатические поля, масс-спектрометрия.

Lanthanide-Boosted Singlet Oxygen from Diverse Photosensitizers along with Potent Photocatalytic Oxidation.

Singlet oxygen (1O2) plays a central role in photochemical and photobiological research. Although many photosensitizers for efficient 1O2 generation were reported, further improving its yield and oxidation power is still highly desirable. Instead of developing new ones, current photosensitizers might be boosted by mediators to facilitate energy transfer. Taking advantage of the long triplet state lifetime of lanthanide ions (Ln3+), we herein demonstrate their roles as potent oxidation mediators. Using oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) at neutral pH as a difficult model reaction, based on the fluorescence, phosphorescence, and metal-binding properties, various dyes and nanomaterials were classified into four types. The 1O2 emission of carbon dots and rose bengal was enhanced 4 times in the presence of Ce3+. Some nonphosphorescent, but strongly fluorescent dyes that are not known as photosensitizers can still be mediated by Ln3+ to produce 1O2, but metal-chelating calcein was not enhanced. Finally, nonemissive dyes failed to show activity. As mediators, the excited Ln3+ can migrate a long distance and transfer energy to O2, resulting in high 1O2 yield. Since redox-active Ce3+ and Eu3+ had the highest activity, participation of oxidation involving excited lanthanides might be possible too. In addition, Ln3+ also enhanced the activity of graphene quantum dots, graphene oxide, and g-C3N4. Rapid degradation of organic dyes was demonstrated, further supporting a high photocatalytic activity of the Ln3+-mediated system.

Degradation Model Considering Electrolyte Dry-out Factor of Lithium Ion Battery and Lifetime Prediction of Combined Battery System for Automotive Application

Degradation Model Considering Electrolyte Dry-out Factor of Lithium Ion Battery and Lifetime Prediction of Combined Battery System for Automotive Application