Decay Of Ions Research Articles

Modeling the Dynamic Global Distribution of the Ring Current Oxygen Ions Using Artificial Neural Network Technique

AbstractThe ring current is an important component of the Earth's near‐space environment, as its variations are the direct driver of geomagnetic storms that can disrupt power grids, satellite communications, and navigation systems, thereby impacting a wide range of technological and human activities. Oxygen ions (O+) are one of the major components of the ring current and play a significant role in both the enhancement and depletion of the ring current during geomagnetic storms. Although a standard statistical study can provide average global distributions of ring current ions, it can't offer insight into the short‐term dynamic variations of the global distribution. Therefore, we employed the Artificial Neural Network technique to construct a global ring current O+ ion model based on the Van Allen Probes observations. Through optimization of the combination of input geomagnetic indices and their respective time history lengths, the model can well reproduce the spatiotemporal variation of the oxygen ion flux distributions and demonstrates remarkable accuracy and minimal errors. Additionally, the model effectively reconstructs the temporal variation of ring current O+ ions for non‐training set data. Furthermore, the model provides a comprehensive and dynamic representation of global ring current O+ ion distribution. It accurately captures the dynamics of O+ ions during a geomagnetic storm with the oxygen ion fluxes enhancement and decay, and reveals distinct characteristics for different energy levels, such as injection from the plasma sheet, outflow from the ionosphere, and magnetic local time asymmetry.

A photon source model for alpha-emitter radionuclides

Objective. A Monte Carlo virtual source model named PHID (photon from Ion decay) that generates photons emitted in the complex decay chain process of alpha-emitter radionuclides is proposed, typically for use during the simulation of SPECT image acquisition. Approach. Given an alpha-emitter radionuclide, the PHID model extracts from Geant4 databases the photon emission lines from all decaying daughters for both isometric transition and atomic relaxation processes. According to a given time range, abundances and activities in the decay chain are considered thanks to the Bateman equations, taking into account the decay rates and the initial abundances. Main results. PHID is evaluated by comparison with analog Monte Carlo simulation. It generates photons with the correct energy and temporal distribution, avoiding the costly simulation of the complete decay chain thus decreasing the computation time. The exact time gain depends on the simulation setup. As an example, it is 30× faster for simulating 1 MBq of 225Ac in water for 1 section Moreover, for 225Ac, PHID was also compared to a simplified source model with the two main photon emission lines (218 and 440 keV). PHID shows that 2 times more particles are simulated and 60% more counts are detected in the images. Significance. PHID can simulate any alpha-emitter radionuclide available in the Geant4 database. As a limitation, photons emitted from Bremsstrahlung are ignored, but they represent only 0.7% of the photons above 30 keV and are not significant for SPECT imaging. PHID is open-source, available in GATE 10, and eases the investigation of imaging photon emission from alpha emitters.

Determining Collisional Cross Sections from Ion Decay with Individual Ion Mass Spectrometry.

Collision cross section (CCS) measurements determined by ion mobility spectrometry (IMS) provide useful information about gas-phase protein structure that is complementary to mass analysis. Methods for determining CCS without a dedicated IMS system have been developed for Fourier transform mass spectrometry (FT-MS) platforms by measuring the signal decay during detection. Individual ion mass spectrometry (I2MS) provides charge detection and measures ion lifetimes across the length of an FT-MS detection event. By tracking lifetimes for entire ion populations, we demonstrate simultaneous determination of charge, mass, and CCS for proteins and complexes ranging from ∼8 to ∼232 kDa.

Highly cyto- and immune compatible new synthetic fluorapatite nanomaterials co-doped with rubidium(I) and europium(III) ions

In the present study, biocompatible luminescent of nanosized fluorapatite doped with rubidium(I) (Rb+ ion) and europium(III) (Eu3+ ion) ions were synthesized via hydrothermal method. It was investigated the influence of co-doped Rb+ and Eu3+ ions on the structural, and morphological characteristics of the obtained fluorapatite materials. The characterization techniques utilized included: X-ray powder diffraction (XRPD), infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). Moreover, to establish the influence of the co-doped Rb+ and Eu3+ ions on the luminescence properties of the lanthanide ion, emission excitation, emission spectrum and luminescence decays were measured. This confirmed a distinct red emission originating from Eu3+ ions and an increased emission lifetime. To determine the biocompatibility of the obtained fluorapatite compounds, in vitro studies using normal dermal human fibroblasts were performed. The results of these studies clearly demonstrate the remarkable biocompatibility of our compounds. This discovery opens exciting prospects for the use of synthetic fluorapatites doped with Eu3+ and Rb+ ions in various biomedical contexts. In particular, these materials hold great promise for potential applications in regenerative engineering, but also serve as innovative and practical solutions as bone scaffolds and dental implants containing nano-fluorapatite. Further discussion of these properties can be found in this article, along with a discussion of their importance and potential in the field of biomedical applications. However, according to our pervious study and based on our current investigations but also based on available scientific records, it was proposed potential molecular mechanism of Rb+ ions in the process of osteoclastogenesis.

Quantum Chemical Analysis of Molecular and Fragment Ions Produced by Field Ionization of Methyl Stearate.

The formation of molecular and fragment ions observed in the field ionization mass spectrum of methyl stearate has been analyzed on the basis of quantum chemical calculations including time-dependent density functional theory (TDDFT) and natural bond orbital (NBO) analysis. The TDDFT calculations suggest that methyl stearate is ionized via two processes, namely a 7.43 eV excitation and a tunneling effect, while the high electric field of 1010 V/m enables analyte molecules to ionize at an effective 6 eV lower than the 9.26 eV ionization energy. The NBO analysis suggests that the abundances of aliphatic fragment ions [CnH2n+1]+ at m/z 29, 43, and 57 generated in the ionizing cell can be rationalized by hyperconjugation between the sigma (σ)-electrons of sp3 C-H bonds of methyl or methylene groups and the empty p-orbital of the carbocation -CH2+. The C4 periodic methyl ester fragment ions at m/z 115-269 and the complementary McLafferty rearrangement fragment ion at m/z 224 can be explained by metastable ion decay with rearrangement reactions in the ion source.

Spectroscopic properties of Cr2+ ions in Zn1-xMnxSe solid solutions

The spectroscopic properties of Cr2+ ions in a range of cubic Zn1-xMnxSe (x = 0–0.4) solid solutions were investigated. An almost linear decrease in 5E level energy was observed, resulting in both absorption and fluorescence maxima shifts of approximately 30 cm−1 per 10 % of Mn. The temperature dependence of Cr2+ ion decay time was studied, and an increase in nonradiative quenching rate was revealed when Mn concentration (x) increased. The position of the Cr2+ ions zero-phonon line (about 4871 cm−1) in the Zn1-xMnxSe (x = 0.4) crystal was determined.

Electron Capture Dissociation by Triclocarban Molecules

The formation and decay of molecular negative ions (MNIs) formed during resonant scattering of electrons by triclocarban molecules were studied by dissoiative electron attachment (DEA) spectroscopy. The most intense channel observed in the mass spectrum are MNIs formed at the thermal energy of trapped electrons with a lifetime relative to electron autodetachment of ~2800 μs. The experimental results were interpreted using CAM-B3LYP/6-311+G(d,p) calculations, which made it possible to reveal a number of important features of the geometry of molecular and fragment negative ions. Namely, the most stable geometry of MNIs is such that one of the chlorine atoms is coordinated with two hydrogen atoms of the structural element of urea. The charge on the chlorine atom is ~–0.7e–, which allows us to interpret this state as the result of the “roaming” of the chlorine atom in the MNI. According to calculations, the adiabatic electron affinity (EAa) of the triclocarban molecule is 1.66 eV. Evaluation of EAa in a simple Arrhenius approximation gives 1.2–1.4 eV. An analysis of the potential of the appearance of fragment ions with a C6H3Cl2NH2 structure made it possible to discover the noncovalent structure of these pseudo-MNIs, in which the chlorine atom is coordinated with two hydrogen atoms of the amino group.

Charge Migration in HCCI Cations Probed by Strong Field Ionization: Time-Dependent Configuration Interaction and Vibrational Wavepacket Simulations.

Strong field ionization of neutral iodoacetylene (HCCI) can produce a coherent superposition of the X and A cations and results in charge migration between the CC π orbital and the iodine π-type lone pair. This charge migration causes oscillations in the rate of strong field ionization of the cation to the dication that can be monitored using intense few-cycle probe pulses. The dynamics and strong field ionization of the coherent superposition the X and A states of HCCI+ have been modeled by time-dependent configuration interaction (TDCI) simulations. When the nuclei are allowed to move, the electronic wavefunctions need to be multiplied by vibrational wavefunctions. Nuclear motion has been modeled by vibrational packets moving on quadratic approximations to the potential energy surfaces for the X and A states of the cation. The overlap of the vibrational wavepackets decays in about 10-15 fs. Consequently, the oscillations in the strong field ionization decay on the same time scale. A revival of the vibrational overlap and in the oscillations of the strong field ionization is seen at 60-110 fs. TDCI simulations show that the decay and revival of the charge migration can be monitored by strong field ionization with intense 2- and 4-cycle linearly polarized 800 nm pulses. The revival is also seen with 7-cycle pulses.

Mass Spectra of New Heterocycles: XXVI. Electron Impact and Chemical Ionization Study of N-[5-Amino-2-thienyl]- and N-[2-(Methylsulfanyl)-1,3-thiazol-5-yl]isothioureas

The behavior of a representative series of previously unknown N -(5-amino-2-thienyl)- and N -[2-(methylsulfanyl)-1,3-thiazol-5-yl]isothioureas under electron ionization (70 eV) has been studied for the first time. 2-Thienylisothioureas form a fairly stable molecular ion ( I rel 11-25%), whereas there are no peaks of molecular ions in the mass spectra of 1,3-thiazolylisothioureas. The common direction of the decay of the molecular ion of 2-thienyl- and 1,3-thiazolylisothiourea is the breaking of the C-N bond in the isothiourea fragment with the localization of the charge on the imine nitrogen atom and the formation of the ion [R3SC≡NR2]+ ( I rel 34-100%), and for thienyl derivatives also the ion [ M - R3SC=NR2]+ (with the localization of the charge on the amine nitrogen atom). Moreover, the last ion is the main one ( I rel 91-100%). Peaks of [ M - MeSCN]+• and [MeSCS]+ ions have also been identified in the spectra of 1,3-thiazolylisothioureas, the appearance of which is associated with the decay of the thiazole cycle in a molecular ion. In addition, unlike 2-thienylisothioureas, for the studied 1,3-thiazolylisothioureas, there is a break in the Chet-N bond with the localization of the charge on the thiazole-containing fragment.

Controlling the charge of dust particles in a plasma afterglow by timed switching of an electrode voltage

A method is demonstrated for controlling the charge of a dust particle in a plasma afterglow, allowing a wider range of outcomes than an earlier method. As in the earlier method, the dust particles are located near an electrode that has a DC voltage during the afterglow. Here, that DC voltage is switched to a positive value at a specified delay time, instead of maintaining a constant negative voltage as in the earlier method. Adjusting the timing of this switching allows one to control the residual charge gradually over a wide range that includes both negative and positive values of charge. For comparison, only positive residual charges were attained in the earlier method. We were able to adjust the residual charge from about −2000 e to +10 000 e, for our experimental parameters (8.35 µm particles, 8 mTorr argon pressure, and a DC voltage that was switched from −150 V to +125 V within the first two milliseconds of the afterglow). The plasma conditions near the dust particles changed from ion-rich to electron-rich, when the electrode was switched from cathodic to anodic. Making this change at a specified time, as the electrons and ions decay in the afterglow, provides this control capability. These results also give insight into the time development of a dust particle’s charge in the afterglow, on a sub-millisecond time scale.

Expanding Orbitrap Collision Cross-Section Measurements to Native Protein Applications Through Kinetic Energy and Signal Decay Analysis.

The measurement of collision cross sections (CCS, σ) offers supplemental information about sizes and conformations of ions beyond mass analysis alone. We have previously shown that CCSs can be determined directly from the time-domain transient decay of ions in an Orbitrap mass analyzer as ions oscillate around the central electrode and collide with neutral gas, thus removing them from the ion packet. Herein, we develop the modified hard collision model, thus deviating from the prior FT-MS hard sphere model, to determine CCSs as a function of center-of-mass collision energy in the Orbitrap analyzer. With this model, we aim to increase the upper mass limit of CCS measurement for native-like proteins, characterized by low charge states and presumed to be in more compact conformations. We also combine CCS measurements with collision induced unfolding and tandem mass spectrometry experiments to monitor protein unfolding and disassembly of protein complexes and measure CCSs of ejected monomers from protein complexes.

Comparing the kinetics of ionized and neutral atoms from single and multi-element laser-produced plasmas

Kinetics of ion and neutral atom emission features were compared for nanosecond laser-produced plasmas generated from several metal targets (i.e., Al, Ti, Zr, Nb, Ta) and an alloy containing all of these as principal alloying elements. Plasmas were produced by focusing 6 ns, 1064 nm pulses from an Nd:YAG laser on the targets of interest in a vacuum. A Faraday cup was used for collecting ion temporal features while spatially and temporally resolved emission spectroscopy was used for measuring the optical time of flight of various neutral atomic transitions. Our results highlight that most probable ion and atom velocities decay with increasing atomic mass. Trends for ions from the alloy target represent a weighted average where all ions contribute. For both ions and atoms, velocities decrease with increasing heat of vaporization and melting temperature, consistent with the thermal mechanisms that contribute to nanosecond laser ablation. Kinetic energies for neutral atoms from pure metal targets have some variability with atomic mass, whereas kinetic energies for atoms from the alloy target are more similar. These more similar kinetic energies observed for neutral atoms in the multi-element plasma may be attributed to collisions between species from all elements in the Knudsen layer.

P‐7.2: Suppression of Ion Drop of ITO‐Decapped a:Si‐H TFT for ADS Pro Display

The decay of Ion of ADS Pro‐type TFTs experienced 1ITO decap often brings about a lot of TFT devices scrapped. It is necessary and valuable to identify the reasons and to solve the Ion drop problem induced by decap. In the present work, the difference in procedure and electronic performance between the normal and the decap TFT process was first compared, then a series of controlled and confirmation experiments to get the mechanism of Ion drop were designed and carried out. It is found that not the extra etching, but the additional ITO film deposition procedure in the decap process is the cause of Ion degradation; during ITO deposition process, the plasma cleaning would lead to the plasma damage to the silicon island, and the In and O atoms in ITO target would intrude into the silicon to form p‐type doping or SiOx oxide, giving rise to the decrease of the carrier concentration and the increase of the resistance, which eventually account for the Ion drop. Finally, the measures to suppress the Ion degradation caused by 1ITO decap were proposed and verified, it shows that the decay percentage of Ion will decline from 15% in the normal decap process to 8.9%, 12.2% and 10.6% by turning off the plasma cleaning, cutting down the deposition power, and reducing the ITO annealing temperature, respectively. And when these three above methods are combined introduction together, the Ion drop after decap can be further lower to less than 5%, which meets the requirements of mass production. This study provides a way to suppress Ion degradation and a reference to optimize TFT properties and improve product yield.

Structural, optical behavior and Judd-Ofelt analysis of europium-doped silicophosphate glasses for red-emitting device applications

Silicophosphate glasses doped with europium are of great interest in fundamental fields such as photonics, luminous diodes, optoelectronics, and lasers. In the present study, we have focused on exploring the effect of the europium (Eu3+) dopant on the structural, physical, and optical properties of silicophosphate glasses. In this study, pure and europium-doped silicophosphate glasses were synthesized by using the sol-gel method. To evaluate the structural and optical properties of the prepared glasses, X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible spectroscopy, photoluminescence spectra, and luminescence decay of trivalent europium ions in glasses were examined. XRD revealed that all of the synthesized glasses contained amorphous phases. FTIR transmittance spectra demonstrated that the addition of europium in the silicophosphate glass leads to a reduction in the dimensionality of the network as a result of the rupture of the Si–O–Si bonds into their structure. The band gap energy of the samples increases with the dopant of europium. The photoluminescence spectrum shows the line characteristics of the Eu (III) ion 5D0→7FJ (J = 0, 1, 2, 3 and 4). Large bands were observed, suggesting non-homogeneous sites that are characteristics of amorphous systems. The intensity parameters ΩJ (J = 2, 4) and the radiative properties of Eu3+ ions in the prepared glasses, such as the stimulated emission cross-section (σe), transition probability (A), radiative lifetime (τcal), and branching ratio (βR) were determined, and Eu3+ emission may be suggested for suitable laser applications due to its high value of βR=52.71%. Furthermore, the CIE 1931 color coordinates of the synthesized glass (x, y) are within the range of (0.63, 0.36) and are quite close to the standard red color (0.67, 0.33), indicating that pure bright red emission has been achieved. The obtained results show that the europium-doped silicophosphate glasses can be appropriate for use as a red laser material.

Cascading parametric decay coupling between whistler and ion acoustic waves: Darwin particle-in-cell simulations

We present the results of numerical studies of the whistler wave parametric decay instability in the system with the suppressed Landau damping of ion acoustic waves (IAWs) based on the self-consistent Darwin particle-in-cell (PIC) model. It has been demonstrated that a monochromatic whistler wave launched along the background magnetic field couples to a counter-propagating whistler mode and co-propagating ion acoustic mode. The coupling of the electromagnetic mode to the electrostatic mode is guided by a ponderomotive force that forms spatio-temporal beat patterns in the longitudinal electric field generated by the counter-propagating whistler and the pump whistler wave. The threshold amplitude for the instability is determined to be δBw/B0 = 0.028 and agrees with a prediction for the ion decay instability: δBw/B0 = 0.042 based on the linear kinetic damping rates, and δBw/B0 = 0.030 based on the simulation derived damping rates. Increasing the amplitude of the pump whistler wave, the secondary and tertiary decay thresholds are reached, and cascading parametric decay from the daughter whistler modes is observed. At the largest amplitude (δBw/B0 ∼ 0.1) the primary IAW evolves into a short-lived and highly nonlinear structure. The observed dependence of the IAW growth rate on the pump wave amplitude agrees with the expected trend; however, quantitatively, the growth rate of the IAW is larger than expected from theoretical predictions. We discuss the relevant space regimes where the instability could be observed and extensions to the parametric coupling of whistler waves with the electron acoustic wave (EAW).

Dissociative electron attachment to p-fluoranil and p-chloranil.

The processes of formation and decay of negative molecular ions (NMI) of p-fluoranil [2,3,5,6-tetrafluoro-1,4-benzoquinone (FA)] and p-chloranil [2,3,5,6-tetrachloro-1,4-benzoquinone (CA)] in the gas phase were investigated. In both cases, long-lived NMIs were found in two resonances, at thermal electron energies and in the region of 0.8-0.9eV, with lifetimes relative to electron ejection of τa ∼ 600 µs. The dissociation of molecular NIs with the formation of fragment ions [M-COF2]-, [M-CO]-, and Cl- proceeds at microsecond times, which is confirmed by the registration of the corresponding metastable ions. It is shown that the dependence of the lifetime of MNIs on the electron energy can be explained by the presence of a transition state at an energy of ∼0.5eV.

Dissociative Electron Attachment to Hexachlorobenzene.

Gas phase molecules of hexachlorobenzene (C6 Cl6 ) were investigated by means of dissociative electron attachment spectroscopy (DEAS). Three channels of molecular negative ions decay have been identified: abstraction of Cl- and Cl2- as well as electron detachment (τa ∼250 μs at 343 K). All three channels exhibit temperature dependence. The adiabatic electron affinity estimated using a simple but typically accurate Arrhenius model (EAa =1.6-1.9 eV) turns out to be much higher than the quantum-chemical predictions (EAa =0.9-1.0 eV). We discuss the possible reasons behind the observed discrepancy.

Heat treatment and fiber drawing effect on the luminescence properties of RE-doped optical fibers (RE = Yb, Tm, Ho).

We investigate the influence of various optical fiber fabrication processes on the fluorescence decay of RE ions commonly used in fiber lasers and amplifiers, i.e. Yb3+, Tm3+ and Ho3+. Optical fiber preforms were prepared using the MCVD method combined with Al2O3 nanoparticle doping and subjected to subsequent heat treatment processes such as preform elongation and fiber drawing. The fluorescence decay of RE ions was measured in multiple stages of optical fiber preparation: in an original preform, in an elongated preform (cane), in a standard fiber, and in an overcladded fiber. It was found that heat treatment processing of the preforms generally leads to a faster fluorescence decay, which can be explained by the diffusion of dopants and clustering of RE ions. The fiber drawing exhibited a greater effect compared to preform elongation, which was ascribed to a faster cooling rate of the process. In general, the heat treatment of RE-doped silica glass preforms leads to the decline of fluorescence decay.

Cu2+ and Cu3+ acceptors in β-Ga2O3 crystals: A magnetic resonance and optical absorption study

Electron paramagnetic resonance (EPR) and optical absorption are used to characterize Cu2+ (3d9) and Cu3+ (3d8) ions in Cu-doped β-Ga2O3. These Cu ions are singly ionized acceptors and neutral acceptors, respectively (in semiconductor notation, they are Cu− and Cu0 acceptors). Two distinct Cu2+ EPR spectra are observed in the as-grown crystals. We refer to them as Cu2+(A) and Cu2+(B). Spin-Hamiltonian parameters (a g matrix and a 63,65Cu hyperfine matrix) are obtained from the angular dependence of each spectrum. Additional electron-nuclear double resonance (ENDOR) experiments on Cu2+(A) ions give refined 63Cu and 65Cu hyperfine matrices and provide information about the nuclear electric quadrupole interactions. Our EPR results show that the Cu2+(A) ions occupy octahedral Ga sites with no nearby defect. The Cu2+(B) ions, also at octahedral Ga sites, have an adjacent defect, possibly an OH− ion, an oxygen vacancy, or an H− ion trapped within an oxygen vacancy. Exposing the crystals at room temperature to 275 nm light produces Cu3+ ions and reduces the number of Cu2+(A) and Cu2+(B) ions. The Cu3+ ions have an S = 1 EPR spectrum and are responsible for broad optical absorption bands peaking near 365, 422, 486, 599, and 696 nm. An analysis of loops observed in the Cu3+ EPR angular dependence gives 2.086 for the g value and 22.18, 3.31, and −25.49 GHz for the principal values of D (the fine-structure matrix). Thermal anneal studies above room temperature show that the Cu3+ ions decay and the Cu2+ ions recover between 75 and 375 °C.

Нековалентные структуры отрицательных ионов, образующиеся при диссоциативном захвате электронов молекулами

The method of dissociative electron attachment (DEA) spectroscopy was used to study the attachment of electrons to 1-chloronaphthalene molecules. It has been established that the dominant channel for the decay of molecular ions is the formation of Clˉ ions in three resonances at 0.7, 1.5, and 3.0 eV. Ions [M-H]ˉ and [M-Cl]ˉ are observed at energies from 3.5 to 8.5 eV and have two to three orders of magnitude lower formation cross sections. Long-lived molecular ions were not registered. Calculations in the DFT CAM B3LYP/6-311+G(d,p) approximation predict the presence of six stable anionic structures in which the chlorine anion is coordinated to the neutral residue via noncovalent H–Clˉ–H bonds. The electron affinity of the most stable of these structures coincides with the experimentally measured value EAa=0.2771±0.003 eV. These results agree with the previously obtained data on the DEA of molecules of bromine-substituted biphenyls, naphthalenes, and anthracenes and confirm the existence of anionic structures with non-covalent H–Hal–H bonds. Such non-covalent anion structures should be extremely reactive, which makes them promising for the synthesis of self-assembling hydrocarbon nanomembranes.