Search results for "SPECT"
showing 10 items of 28650 documents
On-line commissioning of SHIPTRAP
2006
Abstract The on-line commissioning of the Penning-trap mass spectrometer SHIPTRAP was successfully completed with a mass measurement of holmium and erbium radionuclides produced at SHIP. A large fraction of contaminant ions created in the stopping cell was identified to originate from the buffer-gas supply system. Using a liquid nitrogen cold trap they were reduced to a tolerable amount and mass measurements of Er 147 , Er 148 , and Ho 147 with relative uncertainties of about 1 × 1 0 − 6 were performed.
Direct mass measurements and ionization potential measurements of the actinides
2019
Abstract The precise determination of atomic and nuclear properties such as masses, differential charge radii, nuclear spins, electromagnetic moments and the ionization potential of the actinides has been extended to the late actinides in recent years. In particular, laser spectroscopy and mass spectrometry have reached the region of heavy actinides that can only be produced only at accelerator facilities. The new results provide deeper insight into the impact of relativistic effects on the atomic structure and the evolution of nuclear shell effects around the deformed neutron shell closure at N = 152. All these experimental activities have also opened the door to extend such measurements t…
Measurement of the laser resonance ionization efficiency for lutetium
2019
Abstract The development of a highly efficient resonance ionization scheme for lutetium is presented. A laser ion source, based on the all-solid-state Titanium:sapphire laser system, was used at the 30 keV RISIKO off-line mass separator to characterize different possible optical excitation schemes in respect to their ionization efficiency. The developed laser resonance ionization scheme can be directly applied to the use at radioactive ion beam facilities, e. g. at the CERN-MEDICIS facility, for large-scale production of medical radioisotopes.
The Taming of Redox‐Labile Phosphidotitanocene Cations
2019
International audience; Tame d0 phosphidotitanocene cations stabilized with a pendant tertiary phosphane arm are reported. These compounds were obtained by one-electron oxidation of d1 precursors with [Cp2Fe][BPh4]. The electronic structure of these compounds was studied experimentally (EPR, UV/Vis, and NMR spectroscopy, X-ray diffraction analysis) and through DFT calculations. The theoretical analysis of the bonding situation by using the electron localization function (ELF) shows the presence of π-interactions between the phosphido ligand and Ti in the d0 complexes, whereas dπ–pπ repulsion prevents such interactions in the d1 complexes. In addition, CH–π interactions were observed in seve…
Towards Atomically Precise Supported Catalysts from Monolayer‐Protected Clusters: The Critical Role of the Support
2020
Abstract Controlling the size and uniformity of metal clusters with atomic precision is essential for fine‐tuning their catalytic properties, however for clusters deposited on supports, such control is challenging. Here, by combining X‐ray absorption spectroscopy and density functional theory calculations, it is shown that supports play a crucial role in the evolution of monolayer‐protected clusters into catalysts. Based on the acidic nature of the support, cluster‐support interactions lead either to fragmentation of the cluster into isolated Au–ligand species or ligand‐free metallic Au0 clusters. On Lewis acidic supports that bind metals strongly, the latter transformation occurs while pre…
Unveiling the Occurrence of Co(III) in NiCo Layered Electroactive Hydroxides: The Role of Distorted Environments
2020
Co- and Ni-based layered hydroxides constitute a unique class of two-dimensional inorganic materials with exceptional chemical diversity, physicochemical properties and outstanding performance as supercapacitors and overall water splitting catalysts. Recently, the occurrence of Co(III) in these phases has been proposed as a key factor that enhance their electrochemical performance. However, the origin of this centers and control over its contents remains as an open question. We employed the Epoxide Route to synthesize a whole set of α-NiCo layered hydroxides. The PXRD and XAS characterization alert about the occurrence of Co(III) as a consequence of the increment in the Ni content. DFT+U si…
Phosphasalen group IV metal complexes: synthesis, characterization and ring opening polymerization of lactide.
2020
International audience; We report the synthesis of a series of Zr and Ti complexes bearing phosphasalen which differs from salen by the incorporation of two P atoms in the ligand backbone. The reaction of phosphasalen proligands (1a-1c)H2 with Zr(CH2Ph)4 led to different products depending on the nature of the N,N-linker in the ligand. In case of ethylene-linked phosphasalen, octahedral Zr complex 2a formed as a single stereoisomer in trans geometry. With the phenylene linker, it was shown by dynamic NMR spectroscopy that complex 2b exists as a mixture of trans and cis-β isomers in solution, both enantiomers (Δ and Λ) of the cis-β isomer being in fast equilibrium with respect to the NMR tim…
9,10-Phenanthrenedione as Visible-Light Photoredox Catalyst: A Green Methodology for the Functionalization of 3,4-Dihydro-1,4-Benzoxazin-2- Ones thro…
2018
A visible-light photoredox functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones through a Friedel-Crafts reaction with indoles using an inexpensive organophotoredox catalyst is described. The reaction uses a dual catalytic system that is formed by a photocatalyst simple and cheap, 9,10-phenanthrenedione, and a Lewis acid, Zn(OTf)2. 5W white LEDs are used as visible-light source and oxygen from air as a terminal oxidant, obtaining the corresponding products with good yields. The reaction can be extended to other electron-rich arenes. Our methodology represents one of the most valuable and sustainable approach for the functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones, as compared to th…
High-resolution rovibrational spectroscopy of c-C3H2+: The ν7 C–H antisymmetric stretching band
2020
Abstract The ν 7 antisymmetric C–H stretching fundamental of c- C 3 H 2 + has been characterized in a cryogenic 22-pole ion trap by a novel type of action spectroscopy, in which the rovibrational excitation of c- C 3 H 2 + is detected as a slowing down of the low-temperature reaction c- C 3 H 2 + + H2 → C 3 H 3 + + H. Ninety-one rovibrational transitions with partly resolved fine structure doublets were measured in high resolution. Supported by high-level quantum chemical calculations, spectroscopic parameters were determined by fitting the observed lines with an effective Hamiltonian for an asymmetric rotor in a doublet electronic ground state, X ˜ A 1 2 , yielding a band origin at 3113.6…
Tuning the Electronic Properties of Nonplanar exTTF-Based Push–Pull Chromophores by Aryl Substitution
2012
International audience; A new family ofπ-extended tetrathiafulvalene (exTTF) donor−acceptorchromophores has been synthesized by [2 + 2] cycloaddition of TCNE with exTTF-substituted alkynes and subsequent cycloreversion. X-ray data and theoretical calculations,performed at the B3LYP/6-31G**level, show that the new chromophores exhibit highlydistorted nonplanar molecular structures with largely twisted 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) units. The electronic and optical properties, investigated by UV/visspectroscopy and electrochemical measurements, are significantly modified when theTCBD acceptor unit is substituted with a donor phenyl group, which increases the twistingof the TCBD unit…