Resonance Ion Research Articles

Resonance multiphoton ionization of alkaline Earth Ca, Ba, Sr atoms

In this work, we study the process of three-photon resonant ionization of alkaline earth atoms Ca, Sr, and Ba. To carry out the experiments, a frequency-tunable laser setup was created. An effusive beam of alkali atoms served as an atomic target.

Detection of ship emissions from distillate fuel operation via single-particle profiling of polycyclic aromatic hydrocarbons

A novel marker approach can detect individual particles from ship emissions in the atmosphere via resonant ionization of aromatic hydrocarbons.

Resonance ionization spectrum of autoionization states of lutetium atom

<sup>177</sup>Lu is an important medical isotope used in imaging-guided radiotherapy, and it can be produced by irradiating <sup>176</sup>Lu or <sup>176</sup>Yb with high abundance. With an increasing demand for medical isotopes, it is very essential to improve the supply capacity for <sup>177</sup>Lu. The multi-step multi-color photoionization method is an effective method to obtain isotopes, and the information of odd-parity autoionization levels is essential. Laser resonance ionization spectroscopy is one of a few spectroscopic experimental methods that can study autoionization levels. An experimental system is developed for the frontier spectroscopic research, and it consists of custom-made tunable lasers and a high-resolution time of flight mass spectrometer. The lifetime of the excited state 35274.5 cm<sup>–1</sup> is measured to be (31.6 ± 1.7) ns by the delayed photoionization method for the first time. A three-step three-color photoionization process is used to detect the autoionization levels, with a delay of 30 ns between <i>λ</i><sub>2</sub> – <i>λ</i><sub>1</sub> and <i>λ</i><sub>3</sub> – <i>λ</i><sub>2</sub> respectively, in order to avoid any unexpected transitions. Forty-seven odd-parity autoionization levels are obtained, of which 33 levels are discovered for the first time, and the <i>λ</i><sub>2</sub> and <i>λ</i><sub>1</sub> are blocked to exclude possible interference peaks, such as the <i>λ</i><sub>1</sub>+<i>λ</i><sub>3</sub>+<i>λ</i><sub>3</sub> transition. Several autoionization levels show asymmetrical peak shapes, and the Fano fitting is carried out for all the levels to determine the widths and relative transition strengths of the autoionizing transitions. This study provides critical data for the high-efficient photoionization of lutetium atoms in the visible range. The angular momenta of 21 odd-parity autoionization levels in an energy range of 50650–51650 cm<sup>–1</sup> are identified for the first time, which provides a reference for determining the forbidden state of electric dipole transitions from other excited states and ascertaining the electronic configuration.

Experimental study on 10-cm ECRIT neutralizer with nitrogen gas

Electron cyclotron resonance ion thruster (ECRIT) with a diameter of 10 cm can be operated in multiple types of gases and it is feasible to be applied to air-breathing electric propulsion systems. The study on the neutralizer of the ECRIT running in nitrogen gas is the basis for the study on the ECRIT running in nitrogen-oxygen mixed gas. When the ECR neutralizer of typical 10-cm ECRIT running in xenon gas runs in nitrogen gas, the extracted electron current is reduced, because ions tend to drift out of the neutralizer, due to the lower molecular weight of nitrogen. The typical neutralizer is no longer suitable for running in nitrogen gas. In this work, based on the 10-cm typical ECR neutralizer, in order to inhibit ions drifting out of the neutralizer and improve the performance of electron extraction, a bipolar ECR neutralizer suitable for running in nitrogen gas is experimentally studied. The results show that under the conditions of gas mass flow rate of 0.04 mg/s and input power of 10 W, the anode voltage required by the typical ECR neutralizer running in nitrogen gas is 150 V when the extracted electron current is 134 mA. However, the bipolar ECR neutralizer requires only 50-V anode voltage, which decreases by about 67%. When the anode voltage is 40V, the power loss of the typical ECR neutralizer is 1204.82 W/A, while the power loss of the bipolar ECR neutralizer is 95.23 W/A, which is about 8.3% of the former. The ion shielding effect of the bipolar ECR neutralizer running on nitrogen gas is remarkable and the electron extraction performance is improved.

Study on the effect of discharge chamber length on the performance of electron cyclotron resonance ion thruster

Discharge chamber length is one of the factors in optimizing the electron cyclotron resonance ion thruster performance. It adjusts the distance between bulk plasma and grid system to change the plasma density upstream of the screen grid, which will affect the ion beam current and focusing state to achieve optimization purpose. However, new evidence shows the discharge chamber length plays an important role in ionization during ion beam extraction, which means that the effect of discharge chamber length on the performance of electron cyclotron resonance ion thruster should be reexamined. After applying grid voltages, another high electron temperature region located upstream of the screen grid is observed in the integrated simulation using particle-in-cell with Monte Carlo collision method, but it is not observed in the traditional discharge chamber simulation. It is believed in the paper that the high electron temperature region exists objectively, because the Child-Langmuir sheath will repel electrons moving towards screen grid back to magnetic mirrors again. Those electrons will gain energy from microwave, and finally form a high electron temperature region along the Child-Langmuir sheath. This phenomenon implies that discharge chamber length can adjust the high electron temperature distribution upstream of screen grid to affect the plasma generation. Therefore, in this work, the effect of discharge chamber length on discharge and ion beam performance is systematically studied by adopting the integrated simulation. In this paper, three ion thrusters with different discharge chamber lengths are simulated. Under the conditions of same magnetic field and operation parameters, the comparisons of electron energy gain, plasma parameter distributions and ion beam current among the three ion thrusters are conducted. The results show that shorter discharge chamber length has higher electron energy gain, plasma density and voltage, but smaller ion beam current. This abnormal phenomenon can also be seen experimentally. By analyzing the ionization rate inside the chamber, it can be seen that high-temperature electrons upstream of the screen grid have a significant contribution to ionization. And thus, a little bit longer discharge chamber length with lower plasma density inside the chamber has bigger ion beam current for having higher plasma density upstream of the screen grid. According to this phenomenon, an electron heating mode is proposed: electrons gain energy by reciprocating through the electron cyclotron resonance layer between the Child-Langmuir sheath and magnetic mirrors. This heating mode can be used as a supplement to the electronic constraints outside the magnetic mirrors to improve the energy utilization efficiency of the thruster, which can provide a new insight into the electron cyclotron resonance ion thruster design in the future.

Oscillating Plasmas for Proton- Boron Fusion in Miniature Vacuum Discharge

Earlier, the experiments on the aneutronic proton-boron (pB) fusion in a miniature nanosecond vacuum discharge (NVD) with oscillatory plasma confinement and correspondent α particles yield were presented. In this work, we consider some specific features of oscillatory confinement as a relatively new type of plasma confinement for fusion. Particle-in-cell (PiC) simulations of pB fusion processes have shown that the plasma in NVD, and especially on the discharge axis, is in a state close to a quasineutral one, which is rather different from the conditions in the well-known scheme of periodically oscillating plasma spheres (POPSs) suggested earlier for fusion. Apparently, small-scale oscillations in NVD are a mechanism of resonant ion heating, unlike coherent compressions in the original POPS scheme. Nevertheless, the favorable scaling of the fusion power in NVD turns out to be close to the POPS fusion but differs significantly both in the compression ratio and in the values of the parameter of quasineutrality. In addition, unlike the POPS scheme, PiC simulation reveals that the distribution functions of protons and boron ions in NVD are non-Maxwellian. Therefore, we have an aneutronic pB synthesis in a nonequilibrium plasma remaining “nonignited” on the discharge axis.

Resonant Laser Ionization and Fine-Structure Study of Silver in an Ablation Plume

We report on a laser photo-ionization study of silver in relation to the Selective Production of Exotic Species (SPES) project at INFN-LNL in the off-line laser laboratory. In this study, two dye lasers and an ablation laser operating at 10 Hz are used alongside a time-of-flight mass spectrometer (TOF-MS). Isotopic separation of the natural, stable isotopes 107Ag and 109Ag was clearly observed in the TOF signal. Resonant photo-ionization of silver was achieved with the use of the scheme 4d105s 2S1/2→ 4d105p 2P3/2o→ 4d106d 2D3/2 with transition wavelengths of 328.163 nm and 421.402 nm, respectively. Doppler-suppressed spectroscopy of these transition lines was performed in an ablation plume. Doppler broadening with collinear injection of excitation lasers and the effect of the linewidths of the excitation lasers were investigated. The fine-structure splitting of the level 4d106d 2D (J = 5/2 and J = 3/2) was confirmed to be 186 ± 2 pm, corresponding to 314 ± 3 GHz.

Interplay between beam-driven chirping modes and plasma confinement transitions in spherical tokamak ST40

Experiments on the high field spherical tokamak ST40 have led to the recent observation of interplay between beam-driven modes of sweeping frequency (chirping modes) and transitions to the enhanced global confinement regime (H-mode) and back to the low confinement regime (L-mode). The H-modes of plasma confinement are identified from decreased intensity of Dα signal and from clear distinctions in the edge gradients of the visible plasma boundary (observed as a sharp plasma edge in camera images). The beam-driven chirping modes, identified as ideal magnetohydrodynamics beta-induced Alfvén acoustic eigenmodes modes, are observed in Mirnov coil signals, interferometry, and soft x-ray diagnostics. A moderate amplitude ‘primer’ chirping mode usually precedes an H–L transition. This is followed by a ‘dominant’ chirping mode with higher amplitude during the L-mode. The L–H transition back to the improved confinement occurs on a longer time scale of tens of ms, consistent with the slowing down time scale of fast beam ions. A dramatic decrease in toroidal plasma rotation is systematically observed associated with chirping modes sweeping down to zero frequency. Resonance maps built for the beam-driven chirping modes with the ASCOT (accelerated simulation of charged particle orbits in torodoial devices) code show that the resonant beam ions have orbits near the trapped-passing boundary. The ASCOT modelling assesses how losses of the resonant fast ions caused by the chirping modes with high enough amplitude modify the torque, potentially affecting the plasma rotation.

Characterization and anticancer potential of Withania somnifera fruit bioactives (a native species to Pakistan) using gas chromatography-mass spectrometer, nuclear magnetic resonance and liquid chromatography-mass spectrometry-electrospray ionization.

Withania somnifera (W. somnifera) is a plant with remarkable pharmacological properties. The plant has an impressive profile of medicinal uses in the folk medicine system of several civilizations. This comprehensive study is aimed to characterize phytochemicals in fruit of W. somnifera and tested for anticancer potential to find out active candidate in disease prevention and treatment. The bioactive components from W. somn-ifera fruit were extracted with polar and non-polar solvents. Anticancer potential of the isolated bioactive was assessed against different cancer cell lines through MTT assay and Incucytes imaging analysis. The extracts were characterized for secondary metabolites using GC-MS (gas chromatography-mass spectrometer), LCMS (liquid chromatography-mass spectrometry)-ESI (electrospray Ionization) and 1H-NMR (electrospray Ionization) techniques. Both freeze-dried and rotary evaporator con-densed extracts exhibited anticancer potential against MDA-MB-231, MCF7- SKOV3 and SKBR3 cell lines. The tested extracts have cell growth inhibition potential ag-ainst mammalian cancer cell line. Hexacosanedioic acid purified from -hexane extract through HPLC was inves-tigated for its cytotoxicity against breast cancer cell line SKBR3 by using Incucytes imaging analysis. We found that a variety of bioactive compounds existed in this plant. One identified compound that was not investigated for cytotoxicity in previous studies was purified and its application showed cytotoxicity on breast cancer cell lines. A number of bioactive identified from fruit may have an effective potential for development into chemotherapy drugs.

Metabolomics Work Flow and Analytics in Systems Biology.

Metabolomics is an omics approach of systems biology that involves the development and assessment of large-scale, comprehensive biochemical analysis tools for metabolites in biological systems. This review describes the metabolomics workflow and provides an overview of current analytic tools used for the quantification of metabolic profiles. We explain analytic tools such as mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy, ionization techniques, and approaches for data extraction and analysis.

Degradation of acetaminophen using persulfate activated with P-doped biochar and thiosulfate

• Acetaminophen was rapidly degraded in persulfate/P-doped biochar/thiosulfate system. • A synergistic effect existed among persulfate, p-doped biochar and thiosulfate. • Electron transfer could be responsible for the degradation of acetaminophen. • The system maintained high removal efficiency in the water from difference sources. In the study, p-doped biochar (PBC) was prepared by the pyrolysis of H 3 PO 4 -impregnated cyanobacteria and used together with thiosulfate (TS) to activate persulfate (PS) for the degradation of acetaminophen (ACP). The biochar was characterized and the results showed that H 3 PO 4 treatment had a pronounced effect on the surface structure and chemical composition of biochar. ACP (0.05 mmol/L) could be completely removed within 90 min under the optimal conditions: 2.0 mmo/L of PS, 0.1 g/L of PBC and 2.0 mmol/L of TS. A synergistic effect existed among PS, PBC and TS. The PS/PBC/TS system maintained high removal efficiency for ACP in the water from difference sources and Cl - (< 2.0 mmol/L) had little effect on it. Quenching experiments, electron paramagnetic resonance measurements and ion analysis revealed that free radicals (SO 4 • − and •OH) and singlet oxygen were not the main reactive species and biochar-mediated electron transfer could be responsible for the degradation of ACP. This work provides a novel method for the degradation of pharmaceutical and personal care products through non-radical pathway and will be benefit for the development of efficient persulfate-based advanced oxidation processes.

Laser photo-ionization study of nat Ag using opto-galvanic signal at SPES offline laser lab

Resonant Ionization Laser Ion Source (RILIS) is one of the most advancing techniques for the production of radioactive ion beams (RIBs) in ISOL facilities. SPES project at INFN-LNL is a second generation ISOL facility which aims to produce several isotopes in a couple of years. Within the framework of this project, resonant photo-ionization schemes of several elements are studied in the offline laser lab, to be later implemented in the SPES Laser Ion Source. Silver is one of the elements being studied for the stated purpose. In this article, we report a resonant photo-ionization scheme of silver tested with a hollow cathode lamp (HCL). Evidence of high lying Rydberg states around 60945.32 cm−1 has also been observed by studying the fast opto-galvanic signal detected.

First results of a new quadrupole minimum-B permanent magnet electron cyclotron resonance ion source

The first experimental results of a novel permanent magnet electron cyclotron resonance ion source (ECRIS) with a minimum-B quadrupole magnetic field topology are presented. Bremsstrahlung measurements indicate that the electrons can reach energies of 150–200 keV. Ion charge states up to Ar11+ and Kr15+ were detected in the charge state distributions of the extracted beams. Measurements in pulsed operation mode reveal an afterglow peak, which implies that high charge state ions are confined electrostatically similar to a conventional ECRIS. The potential applications and future development of the ion source are discussed.

The capture of injected 1+ ions in charge breeder electron cyclotron resonance ion source plasma

The capture process of the 1+ ions in charge breeder electron cyclotron resonance ion sources has been attributed to cumulative small-angle scattering of the incident ions in ion–ion collisions with the buffer gas ions. The model results in controversy between the plasma potential and ion temperature values derived from simulations, and those found in the experiments. We demonstrate that the 1+ ion capture process is dominated by the slowing down of the incident ions by the ambipolar plasma potential, which has previously been assigned with a secondary importance. In this revised view, supported by experimental data, the 1+ capture does not depend on the mass of the injected and plasma ion species, or the ion temperature, which resolves the disagreement between modelling and experiments.

An extraction system design with a strongly inhomogeneous electric field for a JYFL electron cyclotron resonance ion source

A new ECR ion source extraction system has been designed. The design is based on the extraction conditions of the JYFL 14 GHz ECRIS, and its performance is compared to the existing extractor via numerical modeling. The aim is to improve the formation and quality of high-intensity ion beams. The plasma and the puller electrodes shape were changed. The plasma electrode has a narrow tip extruding toward the puller. It causes the electric field to increase near the plasma meniscus and subsequent higher ion velocity growth rate, which leads to the beam space charge reduction at fixed current and acceleration voltage. The extractor was developed with the ion optical code IBSimu. The initial beam parameters were taken from the experimental data. The calculations showed that the new extraction system allows to increase the total extracted current without compromising the beam quality. The new design allows the beam formation optimization for lower extraction voltages overcoming the present space charge limit.

Simulation as a Tool for Understanding Experimental Observations—Ion Beam Extraction from an ECRIS

A model for the simulation of ion beam extraction from an electron-cyclotron resonance ion source is proposed. It is based on the simple fact that charged particles follow magnetic field lines. Therefore, magnetic field lines are used to generate initial conditions for ray-tracing. This model reproduces in simulation experimentally obtained results. The importance of correlations in phase-space caused by the magnetic field is shown in the simulation. This model also describes the physics of space-charge and its compensation in the extracted (fast) ion beam by low-energy electrons. Simulation provides the possibility to test theoretical assumptions, as well as to optimize technical designs.

Diagnostics of highly charged plasmas with multicomponent 1+ ion injection.

We establish multicomponent 1+ injection into a charge breeder electron cyclotron resonance ion source and an associated computational procedure as a noninvasive probe of the electron density n_{e}, average electron energy 〈E_{e}〉, and the characteristic times of ionization, charge exchange, and ion confinement of stochastically heated, highly charged plasma. Multicomponent injection allows refining the n_{e}, 〈E_{e}〉 ranges, reducing experimental uncertainty. Na/K injection is presented as a demonstration. The 〈E_{e}〉 and n_{e} of a hydrogen discharge are found to be 600_{-300}^{+600}eV and 8_{-3}^{+8}×10^{11}cm^{-3}, respectively. The ionization, charge exchange, and confinement times of high charge state alkali ions are on the order of 1 ms-10 ms.

Isolation and purification of 12 flavonoid glycosides from Ginkgo biloba extract using sephadex LH-20 and preparative high-performance liquid chromatography.

An efficient and rapid preparative method for the separation and purification of flavonoid glycosides from the Ginkgo biloba extract (GBE) was developed bysephadex LH-20 and preparative high-performance liquid chromatography (HPLC). 40g GBE of 24% flavonoids were loaded onto the sephadex LH-20 column and five fractions (1.15, 2.57, 1.32, 4.45, and 3.31g) at flavonoid content of 72.3, 54.2, 63.5, 51.2, and 59.2% were produced. Ultimately, 12 flavonoid glycosides that are at least purities of 97.7% were obtained from 100mg of each fraction by preparative HPLC. The fraction A, B, and Deach contained two flavonoids, yielded 35, 30, 23, 20, 25, and 25mg, respectively. The fraction C and E each contained three flavonoids, produced 20, 13, 15, 18, 15, and 20mg, respectively. The chemical structures of the purified compounds were identified by nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI/MS).

Electronic excitation spectra of jet-cooled phenyl isocyanate, m-tolyl isocyanate, and p-phenylene diisocyanate: Assignment of the cis and trans rotational isomers.

To assign cis and trans isomers of m-tolyl isocyanate (mTI) and p-phenylene diisocyanate (pPDI) in the electronic excitation transition, we measured the time-of-flight mass-selected resonant ionization spectra of jet-cooled phenyl isocyanate (PI), mTI, and pPDI in the region of the 275nm first ππ* absorption system. In the excitation spectra of jet-cooled mTI and pPDI, cis- and trans-rotational isomers appeared as doublets. Isomers were assigned by analyzing the methyl-group internal rotation for mTI and by applying low-frequency bending vibrations to the mutual exclusion rule between the one- and two-photon spectra for pPDI. The electronic spectra of the three molecules observed in the jet were assigned to the transition to the first ππ* and third singlet excited states with the aid of time-dependent (TD)-B3LYP/aug-cc-pVDZ and TD-CAM-B3LYP/aug-cc-pVDZ calculations. The 0 - 0 band of PI was observed at 36 354cm-1, those of the cis and trans isomers of mTI at 36 018 and 35 853cm-1, respectively, and those of the cis and trans isomers of pPDI at 34 437 and 34 383cm-1, respectively. All vibronic bands were diffuse, probably because of internal conversion to two singlet nπ* states. For mTI, based on changes in the barrier height of methyl-group internal rotation upon excitation, the Hammett-σm of PI was determined to be -0.12.

Photoionization and Photofragmentation Dynamics of I2 in Intense Laser Fields: A Velocity-Map Imaging Study.

The photoionization and photofragmentation dynamics of I2 in intense femtosecond near-infrared laser fields were studied using velocity-map imaging of cations, electrons, and anions. A series of photofragmentation pathways originating from different cationic electronic states were observed following single ionization, leading to I+ fragments with distinct kinetic energies, which could not be resolved in previous studies. Photoelectron spectra indicate that these high-lying dissociative states are primarily produced through nonresonant ionization from several molecular orbitals (MO) of the neutral. The photoelectron spectra also show clear signatures of resonant ionization pathways (Freeman resonances) to low-lying bound ionic states via Rydberg states of the neutral moiety. To investigate the role of these Rydberg states further, we imaged anionic products (I-) formed through ion-pair dissociations of neutral molecules excited to these Rydberg states by the intense femtosecond laser pulse. Collectively, these results shed significant new light on the complex dynamics of I2 molecules in intense laser fields and on the important role of neutral Rydberg states in a full description of strong-field phenomena in molecules.