Search results for " ionization"
showing 10 items of 621 documents
Mononuclear rearrangements of heterocycles in water/β-CD: information on the real site of reaction from structural modifications of substrates and fr…
2007
Abstract The effect of β-cyclodextrin (β-CD) on the reactivity in the base-catalyzed pathway for the rearrangement in water of some ( Z )-hydrazones of 3-benzoyl-1,2,4-oxadiazoles ( 1b – f ) into the relevant triazoles ( 2b – f ) was investigated, finding different behavior as a function of the proton concentration. ESIMS and 1 H NMR data evidence the formation of host – guest complexes. The whole of the experimental and calculated (MM2) data enabled us to draw some intriguing conclusions concerning the influence of the structures of the substrates and the nature of the formed host – guest complexes on the real site of the reaction.
Resolution Characterizations of JetRIS in Mainz Using 164Dy
2022
Atoms 10(2), 57 (2022). doi:10.3390/atoms10020057
A study of VUV emission and the extracted electron-ion ratio in hydrogen and deuterium plasmas of a filament-driven H−/D− ion source
2019
Vacuum ultraviolet (VUV) emission diagnostics for studying differences of electron impact processes in hydrogen and deuterium plasmas are presented. The method is applied to study a filament driven multicusp arc discharge negative ion source by comparing the VUV-emission intensities of different emission bands and extracted currents of H−/D− ions and electrons. It was found that the ratio of coextracted electrons to extracted ions is four times higher for deuterium than for hydrogen. No significant differences of the VUV-spectra or volumetric rates of ionization, excitation, production of high vibrational states, and dissociation were found between the plasmas of the two isotopes. The volum…
Instrumentation for time-of-flight elastic recoil detection analysis
2016
Time-of-flight elastic recoil detection is an ion beam based method to analyze the elemental composition of thin film samples at different depths. In order to improve the mass resolution and to enable kinematic correction a position sensitive gas ionization chamber energy detector was constructed. This detector along with pre-existing timing detectors were connected to a modern fully digitizing data acquisition setup. This thesis describes the design of these instruments, including all aspects from the mechanical design of the gas ionization detector to the algorithm and software development of the digitizing acquisition setup. The performance of the system has been studied with measurements …
Gas phase behavior of radical cations of perfluoroalkyl-1,2,4-triazines: an experimental and theoretical study
2009
Electron ionization mass spectrometry and low-energy collision-induced decomposition reactions occurring in a tridimensional ion trap, together with density functional theory (DFT) calculations on neutrals, even- and odd-electron cations, have been used to study the gas-phase ion chemistry of a series of perfluoroalkyl-1,2,4-triazines. Loss of oxygen, due to thermal degradation occurring before ionization, likely involving the hydroxylamino group, has been observed. Compounds having a carbonyl group at position 6 of the triazine ring fragment in the source by elimination of NO followed by HF or CO. The decomposition pathways occurring due to CID experiments have shown interesting features d…
Efficient, high-resolution resonance laser ionization spectroscopy using weak transitions to long-lived excited states
2017
Laser spectroscopic studies on minute samples of exotic radioactive nuclei require very efficient experimental techniques. In addition, high resolving powers are required to allow extraction of nuclear structure information. Here we demonstrate that by using weak atomic transitions, resonance laser ionization spectroscopy is achieved with the required high efficiency (1%–10%) and precision (linewidths of tens of MHz). We illustrate experimentally and through the use of simulations how the narrow experimental linewidths are achieved and how distorted resonance ionization spectroscopy line shapes can be avoided. The role of the delay of the ionization laser pulse with respect to the excitatio…
Trace Analysis of Plutonium and Technetium by Resonance Ionization Mass Spectrometry Using an Atomic Beam and a Laser Ion Source
1990
A method for low level detection of plutonium and technetium is described with a detection limit of less than 107 atoms. Plutonium is a very toxic element due to its radioactive decay as well as its chemical behaviour. It was released to the environment in large amounts during the fifties and sixties of his century, principally by nuclear-weapon tests and some accidents. As a result about 0.4 − 4 mBq per gram 239Pu(T1/2 = 24390 y), corresponding to 4 × 108 − 4 × 109 atoms, can be found in the Northern Hemisphere in soil samples.
Nano-sized I12L6 Molecular Capsules Based on the [N⋅⋅⋅I+⋅⋅⋅N] Halogen Bond
2017
Summary Self-assembly of pre-organized subunits with a concave overall shape is an effective strategy for the synthesis of supramolecular capsules. We report the synthesis of a cavitand-based hexameric capsule held together solely by 12 robust [N⋅⋅⋅I + ⋅⋅⋅N] halogen bonds and its characterization in solution and in the gas phase via 1 H NMR spectroscopy, diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY), and electrospray ionization mass spectrometry. The [N⋅⋅⋅I + ⋅⋅⋅N] halogen-bonded hexameric capsule was efficiently synthesized from the isolobal metallosupramolecular Ag + capsule by application of the [N⋅⋅⋅Ag + ⋅⋅⋅N] → [N⋅⋅⋅I + ⋅⋅⋅N] cation-exchange reaction.
Mass spectrometric studies on pyridine-piperazine-containing ligands and their complexes with transition metals formed in solution.
2001
Electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) methods were used to study open-chain piperazine-containing ligands (L) and their complexes formed with transition-metal salts. ESI and MALDI measurements were performed with a Fourier transform ion cyclotron resonance (FT-ICR) and a time-of-flight (TOF) mass spectrometer, respectively. Only singly charged complexes, between one ligand and one or several metal ions, were formed in the ESI measurements. Because the net charge was always one, one or several counterions were attached to the complex. Under ESI conditions, the complexes formed between the ligands and metal (Co, Ni, Cu, and Cd) salts were [L + M…
Gas-phase chemistry, recoil source characterization and in-gas-cell resonance laser ionization of actinides at IGISOL
2018
The underlying theme of this thesis focuses on buffer gas purification and relevant gas-phase ion chemistry which critically affects ion beam purity at gas cell-based radioactive ion beam facilities. The achievement of attaining a sub- parts-per-billion level of impurity at the IGISOL facility has enabled subsequent gas cell developments for production of the actinide elements, plutonium and thorium, required for a program of high-resolution optical spectroscopy. Firstly, the construction and characterization of the new IGISOL buffer gas purification system is presented. Off-line ion beam production of plutonium and thorium using in-gas-cell laser resonance ionization combined with filament dispen…