Resonance Ion Research Articles

Actinide Elemental Ratios of Spent Nuclear Fuel Samples by Resonance Ionization Mass Spectrometry.

While resonance ionization mass spectrometry (RIMS) has demonstrated utility in measuring isotopic compositions of elements in complex matrices without the need for chemical separation to remove isobaric interferences, it has had limited application in measuring elemental compositions. The ability to determine elemental compositions via an in situ method like RIMS would be an exceptional asset in spent nuclear fuel analysis, where they are important in assessing reactor histories and whose chemical separation presents a radiological hazard. However, quantitative elemental analysis by RIMS requires special considerations because each element is ionized by its own set of lasers tuned to element specific resonant ionization wavelengths. We present the first comprehensive study of measuring elemental ratios by RIMS in spent nuclear fuel. All actinides produced by neutron capture are enhanced significantly radially from the center to the edge of a fuel pellet. This edge effect is not readily accessible by conventional bulk measurements.

Vibrational Mode-Dependent Circular Dichroism of Jet-Cooled Styrene Oxide.

Vibrational mode-dependent circular dichroism (CD) effects in vibrational CD spectra are often used to determine the handedness of molecules with multiple chiral centers. Here, we investigate vibrational mode-dependent CD effects in the electronic CD spectra of jet-cooled (R)-(+)- and (S)-(-)-styrene oxide obtained by using resonant two-photon ionization CD (R2PICD) spectroscopy. Although most fundamental vibronic bands demonstrated CD signatures consistent with that of the origin band, the overtone and combination bands exhibited opposite CD signatures. Theoretical calculations suggest that CD in fundamental bands are primarily governed by Franck-Condon contributions, whereas Herzberg-Teller contributions, which reflect the influences of vibrational modes on CD values, become more significant in overtone and combination bands. These results underscore the potential of mode-dependent vibronic CD signals in R2PICD spectra for determining the absolute configurations of molecules with multiple chiral centers.

Highly oxidized sesquiterpenoids from Parasenecio rubescens and assessment of their cytotoxicity

A phytochemical investigation of the whole plant of Parasenecio rubescens (S. Moore) Y. L. Chen yielded 14 previously undescribed, highly oxidized bisabolane-type sesquiterpenoids, named pararunines L–Y, along with one known oplopane-type sesquiterpenoid. The structural elucidation of these compounds was accomplished through comprehensive spectroscopic analysis, including nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) techniques. Motivated by traditional uses and previous studies on this genus, all isolated compounds were subjected to in vitro cytotoxicity assays against four human cancer cell lines (MCF-7, Hela, HCT116, and HT-29). Considering that the reported chemical constituents of numerous other species within this genus primarily consist of eremophilane-type sesquiterpenoids, our findings not only expand the structural diversity of bisabolane-type sesquiterpenoids but also contribute valuable scientific evidence to the chemotaxonomy of this genus.

Vibrational assignments and energy analyses of 3,4-difluorophenylacetylene using resonance-enhanced multiphoton ionization and slow electron velocity-map imaging techniques

Here, we report spectroscopic investigations of 3,4-difluorophenylacetylene applying two-color resonant two-photon ionization (2C-R2PI) and slow electron velocity-map imaging (SEVI) techniques. With the assistance of density functional theory (DFT) calculations, vibrational modes of the S0 neutral ground state, S1 first electronic excited state, and D0 cationic ground state were assigned. The adiabatic excitation energy of the S1 ← S0 electronic transition was determined to be 35639 ± 5 cm−1 from the resonance-enhanced multiphoton ionization (REMPI) spectroscopy. Additionally, the adiabatic ionization potential was found to be 72398 ± 5 cm−1 based on the SEVI spectra.

Lebt of the Heavy Ion Linear Accelerator

At the NRC “Kurchatov Institute” (Kurchatov Complex for Theoretical and Experimental Physics), the pulsed linear resonant heavy ion accelerator is being developed. The Low Energy Beam Transport (LEBT) channel transports the beam from a laser-plasma source of multi-charged ions with an A/Z ratio from 4 to 8 (up to Bi27+) to the RFQ. This paper shares the results of the beam dynamics simulation of the LEBT, which ensures the separation of the working fraction of the ion beam and its matching with the RFQ.

Custom GC×GC configuration for the selective isolation or removal of compounds from complex samples

We developed a novel approach to selectively isolate or remove nearly any compound from complex mixtures of volatile organic compounds. This was achieved by customizing a GC×GC system with a Deans switch, a passive splitter, and a custom-made adapter for sample recollection. The new setup was evaluated with 106 standard chemicals covering a wide range of volatility (boiling points: 56 – 343 ⁰C) and polarity (log P: 0.2 – 9.4). The method was used to remove two notorious malodorous compounds from spoiled wine samples. We found that the recovery can be maximized if a custom-made adapter is attached directly on the flame ionization detector port (average recovery rate of 76 ± 7 % for the standards). Eventually, we could selectively isolate or remove chemicals with peaks separated by a minimum distance of 50 ms for the second column throughout the whole chromatographic run. The developed system is expected to mainly be used in the field of flavor and fragrance analysis (i.e., selection of flavors and odorants of interest or removal of off-flavor or malodorous compounds). At present, we can reasonably collect about 100 ng of each single compound and are currently working on sample enrichment to improve our method to isolate sufficient amounts for further chemical analysis (e.g. high sensitivity nuclear magnetic resonance or chemical ionization tandem mass spectrometry).

Experimental and numerical investigation of the Doppler-shifted resonance condition for high frequency Alfvén eigenmodes on ASDEX Upgrade

Abstract The Doppler-shifted resonance condition for high frequency Alfvénic eigenmodes has been extensively studied on ASDEX Upgrade in the presence of one or a combination of two neutral beam injected (NBI) fast ion populations. In general, only centrally deposited NBI sources drive these modes, while off-axis sources globally stabilize the mode activity. For the case of a single central NBI source, the observed trend is: the highest frequency modes are driven by the lowest energy and lowest pitch angle NBI sources, in line with the expectation from the Doppler-shifted resonance condition. The expected mode frequencies are determined analytically from the two-fluid cold plasma dispersion relation and the most unstable frequency relation, while the mode growth rates are estimated using the fast ion slowing down distribution functions from the ASCOT code. The overall mode frequency trend in a source-to-source variation is tracked, although a systematic overestimate of ∼1 MHz is observed. Possible causes of this overestimate include the finite size of the resonant fast ion drift orbit and non-linear effects such as mode sideband formation. Alternatively, the expected mode frequencies are determined by tracking the growth rate maxima trajectories, this method improves the agreement with the experimentally measured values. A combination of two central mode-driving NBI sources results in the suppression of the mode driven by the lowest energy and the lowest pitch angle NBI source. Computing the analytically expected mode frequency following the method outlined above, again, generally tracks the experimentally observed trend. The mode’s Alfvénic nature allows for a practical application to track the core hydrogen fraction by following the mode frequency changes in response to a varying ion mass density. Such application is demonstrated in a discharge where the average ion mass is varied from ∼2m p to ∼1.5m p (where m p is the proton mass) via a hydrogen puff in a deuterium plasma, in the presence of a strong mode activity. The expected mode frequency changes are computed from the existence of the resonance condition, and the values track the measured results with an offset of ∼0.5 MHz. Overall, the results suggest an intriguing possibility to monitor and control the D-T ion fraction in the core of a fusion reactor in real time using a non-invasive diagnostic.

New Isocoumarins from An Endophytic Fungal Strain Diaporthe arengae M2 and Their Antibacterial Activities.

Four new isocoumarin derivatives 12-O-acetyl-isocitreoisocoumarinol (1), (+)-(10R)-O-acetyl-diaportinol (2-a), (-)-(10S)-O-acetyl-diaportinol (2-b), peyroisocoumarin E (3) and new stereoconfigurations of three isocoumarin derivatives desmethyldichlorodiaportinol A (4), threo-monochlorodiaportinol A (5-a), erytheo-monochlorodiaportinol A (5-b), together with nine known ones (6-14), were separated from the rice fermentation of endophytic fungus Diaporthe arengae M2 isolated from Camellia oleifera. The structures of new compounds were determined by extensive spectroscopic analyses including nuclear magnetic resonance (NMR) and high resolution electrospray ionization mass spectroscopy (HR-ESI-MS). Compounds 4, 7, 8, 12, 13 exhibited definite inhibition against five strains of bacteria with the MIC values range from 16 μg/mL to 64 μg/mL.

Laser Spectroscopic Characterization of Supersonic Jet-Cooled 2,6-Diazaindole (26DAI).

The article presents a comprehensive laser spectroscopic characterization of a nitrogen-rich indole derivative, namely, 2,6-diazaindole (26DAI), in the gas phase. A supersonic jet-cooled molecular beam of 26DAI was characterized using two-color resonant two-photon ionization (2C-R2PI) and laser-induced fluorescence spectroscopy (LIF) to investigate the electronic excitation. The S1 ← S0 origin transition was obtained at 33915 cm-1, which was red-shifted from that of one (indole) and two (7-azaindole) nitrogen-containing indole derivatives by 1317 and 713 cm-1, respectively. The molecular orbital and energy analysis for the S1 ← S0 transition shows the significant stabilization of LUMO on subsequent N-insertion, resulting in the lowering of the S1 ← S0 (ππ*) transition energy. The single vibronic level fluorescence spectrum from the vibrationless S1 state of the molecule was recorded. The spectrum displayed an extensive Franck-Condon activity until 2500 cm-1 for the vibrational modes of the S0 state of the 26DAI molecule. The experimental ground state vibrational frequencies were compared to the calculated ones obtained at three different levels of theories. More accurate results were found at DFT B3LYP-D4 than those at the wave function-based MP2 and CCSD levels of theories. Further, the N-H stretching frequency of 26DAI in the S0 state was measured at 3524 cm-1 using fluorescence-dip infrared (FDIR) spectroscopy. The stability of 26DAI against ionization radiation was probed by measuring the two-color photoionization energy (IE2P) of 26DAI at 71866 cm-1. The IE2P value is significantly higher than those of N-poor counterparts (indole and 7-azaindole). The NBO charges and spin density (SD) values of the 26DAI molecule have shown that electronegative N(6) makes the cationic ground state less stable due to the position of the positive centers on the N atom. The results provided insights into the stability of N-rich biomolecules against photodamage. The current investigation can shed light on nature's way of stabilizing biomolecules with a possible N-insertion mechanism.

Fano-line-shape metamorphosis in resonant two-photon ionization

Fano-line-shape metamorphosis in resonant two-photon ionization

Mechanism exploration of ion-implanted epoxy on surface trap distribution: An approach to augment the vacuum flashover voltages

Abstract The augmentation of the epoxy (EP) resin surface to advance flashover performance has become a pivotal point of global interest. This research introduces a novel surface modification method and its mechanism for insulation materials. The research follows an electron cyclotron resonance ion implantation system to subject the surface of EP insulation to ion beams with diverse energies, i.e., 6, 10, 20, 40, 50, and 60 keV for a consistent time of 300 s at an angle of 90°. The experimental phase includes the DC flashover examination under negative polarity. Besides, the simulation phase includes the Monte Carlo model constructed using SRIM software to examine the range and distribution of bombarded ions in the targeted insulation. Results reveal that the flashover properties are affected by the surface potential, surface conductivity, trap distribution, water contact angle, and elemental composition. Likewise, based on the outcomes and theoretical point of view, it is revealed that the bombardment of energetic ions enhances the trap depth, assisting in a reduction in surface conductivity, confining the surface charge movements, and extensively suppressing the secondary electron emission yield. Also, the enhanced trap depth induces homo-charge formation near triple junctions. Synergistically, the factors contribute to high flashover voltages.

Bias disk boost technique for pulsed-operation electron cyclotron resonance ion sources

A simple, effective technique to increase the intensity of multiply charged ions has been developed for pulsed-operation electron cyclotron resonance ion sources (ECRISs). The technique is realized simply by applying an additional boost voltage of about −1 kV to a negative constant voltage on the bias disk. The technique can be applied to general ECRISs by adding electric devices to the bias disk circuit, such as a high-voltage power supply, a fast high-voltage switch, and a diode. The effect of the technique depends on the ion species, and we obtained a maximum ion intensity increase of 66% for O6+ compared with the conventional bias disk method. In particular, the technique can be applied to the existing pulsed-operation ECRISs used at a heavy-ion cancer therapy facility where multi-ion treatment with multiply charged oxygen and neon ions is planned to be introduced.

Probing the Nanonewton Mitotic Cell Deformation Force by Ion-Resonance-Enhanced Photonics Force Microscopy.

Mechanical forces are essential for regulating dynamic changes in cellular activities. A comprehensive understanding of these forces is imperative for unraveling fundamental mechanisms. Here, we develop a microprobe capable of facilitating the measurement of biological forces up to nanonewton levels in living cells. This probe is designed by coating the core of anatase titania particles with amorphous titania and silica shells and an upconversion nanoparticles (UCNPs) layer. Leveraging both antireflection and ion resonance effects from the shells, the optically trapped probe attains a maximum lateral optical trap stiffness of 14.24 pN μm-1 mW-1, surpassing the best reported value by a factor of 3. Employing this advanced probe in a photonic force microscope, we determine the elasticity modulus of mitotic HeLa cells as 1.27 ± 0.3 kPa. Nanonewton probes offer the potential to explore 3D cellular mechanics with unparalleled precision and spatial resolution, fostering a deeper understanding of the underlying biomechanical mechanisms.

Cyclocarysaponins A–J, dammarane-type triterpenoid glycosides from the leaves of Cyclocarya paliurus

Ten previously undescribed dammarane-type triterpenoid glycosides, cyclocarysaponins A-J (1-10), were isolated from the leaves of Cyclocarya paliurus (Batal.) Iljinskaja. The structures of these compounds were characterized through detailed spectroscopic analysis, including 1D and 2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The cytotoxic activities of all isolates were assessed against five human cancer cell lines (Bel-7402, Caski, BGC-823, A2780, and HCT-116). Of the tested compounds, compounds 1, 7, and 9 exhibited selective cytotoxicity against one or more human cancer cell lines.

Breit interaction in dielectronic recombination of hydrogenlike xenon ions: storage-ring experiment and theory

Abstract Electron-ion collision spectroscopy of the KLL dielectronic recombination (DR) resonances of hydrogenlike xenon ions was performed at a heavy-ion storage ring with a resolving power that is competitive with x-ray spectroscopy of inner-shell transitions in highly charged ions. The $$KL_{1/2}L_{1/2}$$ K L 1 / 2 L 1 / 2 , $$KL_{1/2}L_{3/2}$$ K L 1 / 2 L 3 / 2 , and $$KL_{3/2}L_{3/2}$$ K L 3 / 2 L 3 / 2 resonance groups and even parts of their fine structure are individually resolved. The resonance strengths were measured on an absolute scale and compared with results from multi-configuration Dirac–Fock (MCDF) calculations. These are in excellent agreement with the experimental findings when QED effects on the resonance energies and the Breit interaction are considered. As already found for DR of hydrogenlike uranium (Bernhardt et al. in Phys Rev A 83:020701(R), 2011), this interaction is particularly strong for the $$KL_{1/2}L_{1/2}$$ K L 1 / 2 L 1 / 2 resonance group. For U$$^{91+}$$ 91 + , it increases the $$KL_{1/2}L_{1/2}$$ K L 1 / 2 L 1 / 2 DR resonance strength by 40%. For Xe$$^{53+}$$ 53 + , the increase is found to amount to 25%, confirming the prediction that the influence of the Breit interaction grows with increasing nuclear charge. A comprehensive appendix treats the derivation of experimental and theoretical merged-beams recombination rate coefficients for interacting beams of relativistic electrons and ions. Graphical abstract

Electronic Spectrum of α-Hydrofulvenyl Radical (C6H7), and a Simple and Accurate Recipe for Predicting Adiabatic Ionization Energies of Resonance-Stabilized Hydrocarbon Radicals.

Using a combination of resonant two-photon two-color ionization (R2C2PI) and laser-induced fluorescence/dispersed fluorescence spectroscopy, we have examined the 2A″ ← 2A″ transition of the resonance-stabilized α-hydrofulvenyl radical, produced from methylcyclopentadiene dimer in a jet-cooled discharge. Like the related 1,4-pentadienyl and cyclohexadienyl radicals, the α-hydrofulvenyl Ã-state lifetime is orders of magnitude shorter than the predicted f-value implies, indicative of rapid nonradiative decay. The transition is fully allowed by symmetry but considerably weakened by transition moment interference. Intensity borrowing among a' modes brings about static (i.e., Condon) and vibronic (i.e., Herzberg-Teller) moments of similar size, the result being a spectrum substantially less origin-dominated than is usually observed for extensively delocalized radicals. Twenty -state modes and twelve -state modes are identified with high confidence and assignments for several others are suggested. In addition, from a series of two-color appearance potential scans with the -state zero-point level serving as an intermediate, we obtain a field-free adiabatic ionization energy (AIE) of 7.012(1) eV. For a set of 21 resonance-stabilized radicals bearing 5 to 11 carbon atoms, it emerges that the field-free AIE obtained by R2C2PI methods under jet-cooled conditions lies very close to the average of B3LYP/6-311G++(d,p) (with harmonic zero-point energy) and CBS-QB3 0 K calculations, with a mean absolute deviation of only 0.010(7) eV (approximately 1 kJ/mol). On average, this represents a nearly 10-fold improvement in accuracy over CBS-QB3 predictions for the same set of radicals.

Resonance ionization spectroscopy of neodymium for determining a highly efficient two-step ionization scheme

Two-color two-step resonance ionization spectroscopy of neodymium (Nd) was performed to identify more than 120 even-parity autoionizing levels and their candidate J-values. The analysis of the observed autoionizing Rydberg series yielded a value of 44,560.11 (43)stat (2)sys cm−1 as a more accurate ionization potential of Nd. The saturation method was used to measure the transition cross-sections for some intense ionization transitions. From the measured cross-sections, the ionization efficiencies of some two-step ionization schemes were evaluated using the scheme cross-section formula to obtain several promising schemes.

Preparation of halogen-free flame retardant curing agent and its application in epoxy resin

9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-N-Aminoethylpiperazine (DOPO-AEP), a phosphorus and nitrogen intumescent flame retardant curing agent was prepared by using acetonitrile as solvent using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and N-aminoethylpiperazine (AEP) as raw materials. The structure of the flame retardant curing agent DOPO-AEP was analyzed Fourier Transform Infrared Spectrometer (FTIR), Nuclear Magnetic Resonance (NMR) and Electrospray Ionization Mass Spectrometry (ESI-MS), and the synthesis method of the target product was determined. In addition, the content of char residue was determined by thermogravimetric analyzer, and its thermal properties were comprehensively explored, and based on the obtained results, the curable epoxy resin was selected to prepare DOPO-AEP/EP flame retardant composites. According to the amount of DOPO-AEP added product, different proportions of DOPO-AEP/EP flame retardant composites were prepared, and the actual impact of flame retardant properties and mechanical properties of epoxy resin in different proportions was explored. When the content of DOPO-AEP is 35%, the limiting oxygen index of DOPO-AEP/EP reaches 29.9, which has a significant increase compared with the limiting oxygen index of pure epoxy resin of 19.8, but compared with the content of DOPO-AEP of 30%, the limiting oxygen index of DOPO-AEP/EP is 28.7, and there is no significant increase change. Comprehensive analysis shows that when the component content of DOPO-AEP is 30%, the flame retardant system has a tensile strength of 29.0 MPa, an impact strength of 4.5Kj/m2 and a flexural strength of 73.9 MPa, and its limiting oxygen index is as high as 28.7, and the comprehensive performance of the system is the best. By testing the surface morphology of the flame retardant composites after combustion by SEM, it was found that a dense char layer was formed on the surface of the epoxy resin cured char residue and foamed obviously, indicating that the flame retardant curing performance of DOPO-AEP was good.

Valence Electronic Structure of Interfacial Phenol in Water Droplets.

Biochemistry and a large part of atmospheric chemistry occur in aqueous environments or at aqueous interfaces, where (photo)chemical reaction rates can be increased by up to several orders of magnitude. The key to understanding the chemistry and photoresponse of molecules in and "on" water lies in their valence electronic structure, with a sensitive probe being photoelectron spectroscopy. This work reports velocity-map photoelectron imaging of submicrometer-sized aqueous phenol droplets in the valence region after nonresonant (288 nm) and resonance-enhanced (274 nm) two-photon ionization with femtosecond ultraviolet light, complementing previous liquid microjet studies. For nonresonant photoionization, our concentration-dependent study reveals a systematic decrease in the vertical binding energy (VBE) of aqueous phenol from 8.0 ± 0.1 eV at low concentration (0.01 M) to 7.6 ± 0.1 eV at high concentration (0.8 M). We attribute this shift to a systematic lowering of the energy of the lowest cationic state with increasing concentration caused by the phenol dimer and aggregate formation at the droplet surface. Contrary to nonresonant photoionization, no significant concentration dependence of the VBE was observed for resonance-enhanced photoionization. We explain the concentration-independent VBE of ∼8.1 eV observed upon resonant ionization by ultrafast intermediate state relaxation and changes in the accessible Franck-Condon region as a consequence of the lowering of the intermediate state potential energy due to the formation of phenol excimers and excited phenol aggregates. Correcting for the influence of electron transport scattering in the droplets reduced the measured VBEs by 0.1-0.2 eV.

UV wavelength-dependent photoionization quantum yields for the dark 1nπ* state of aqueous thymidine.

Despite the important role of the dark 1nπ* state in the photostability of thymidine in aqueous solution, no detailed ultraviolet (UV) wavelength-dependent investigation of the 1nπ* quantum yield (QY) in aqueous thymidine has been experimentally performed. Here, we investigate the wavelength-dependent photoemission spectra of aqueous thymidine from 266.7 to 240 nm using liquid-microjet photoelectron spectroscopy. Two observed ionization channels are assigned to resonant ionizations from 1ππ* to the cationic ground state D0 (π-1) and 1nπ* to the cationic excited state D1 (n-1). The weak 1nπ* → D1 ionization channel appears due to ultrafast 1ππ* → 1nπ* internal conversion within the pulse duration of ∼180 fs. The obtained 1nπ* quantum yields exhibit a strong wavelength dependence, ranging from 0 to 0.27 ± 0.01, suggesting a hitherto uncharacterized 1nπ* feature. The corresponding vertical ionization energies (VIEs) of D0 and D1 of aqueous thymidine are experimentally determined to be 8.47 ± 0.12 eV and 9.22 ± 0.29 eV, respectively. Our UV wavelength-dependent QYs might indicate that different structural critical points to connect the multidimensional 1ππ*/1nπ* conical intersection seam onto the multidimensional potential energy surface of the 1ππ* state might exist and determine the relaxation processes of aqueous thymidine upon UV excitation.