A high-current electron beam ion trap as an on-line charge breeder for the high precision mass measurement TITAN experiment

The precision of atomic mass measurements in a Penning trap is directly proportional to the charge state q of the ion and, hence, can be increased by using highly charged ions (HCI). For this reason, charge breeding with an electron beam ion trap (EBIT) is employed at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) on-line facility in Vancouver, Canada. By bombarding the injected and trapped singly charged ions with an intense beam of electrons, the charge state of the ions is rapidly increased inside the EBIT. To be compatible with the on-line requirements of short-lived isotopes, very high electron beam current densities are needed. The TITAN EBIT includes a 6 Tesla superconducting magnet and is designed to have electron beam currents and energies of up to 5 A and 60 keV, respectively. Once operational at full capacity, most species can be bred into a He-like configuration within tens of ms. Subsequently, the HCI are extracted, pass a Wien filter to reduce isobaric contamination, are cooled, and injected into a precision Penning trap for mass measurement. We will present the first results and current status of the TITAN EBIT, which has recently been moved to TRIUMF after assembly and commissioning at the Max-Planck-Institute (MPI) for Nuclear Physics in Heidelberg, Germany.     

A correlation study of Li ground state by the MCHF procedure

Results are reported for multiconfiguration Hartree–Fock studies of correlation in the lithium ground state, which maintain orthogonality of orbitals within a configuration. It is shown that when the 1s- and 2s-orbitals are fixed at their Hartree–Fock value, configurations for which Brillouin's theorem holds may be important, particularly for atomic properties other than energy. The Fermi contact term is considered as an example.     

Lifetime of 2s2p 23s 3 P in N II and other allowed triplet transitions

Systematic transition calculations have been performed for all triplet decay channels from 2s2p ²3s ³ P of N II. The lifetime of 0.505 ns compares favourably with experiment. Transitions in absorption from the 2s ²2p ^{2 3} P ground state have also been determined along with a number of other triplet transitions. Length and velocity forms of thef-value are in agreement at the 2–3% level for most transitions.     

Absolutely continuous spectrum for the Anderson model on a product of a tree with a finite graph

We prove the almost sure existence of absolutely continuous spectrum at low disorder for the Anderson model on the simplest example of a product of a regular tree with a finite graph. This graph contains loops of unbounded size.     

Rate and Computational Studies for Pd-NHC-Catalyzed Amination with Primary Alkylamines and Secondary Anilines: Rationalizing Selectivity for Monoarylation versus Diarylation with NHC Ligands

The relative rates of arylation of primary alkylamines with different Pd-NHC catalysts have been measured, as have the relative rates of arylation of the secondary aniline product in an attempt to understand the key ligand design features necessary to have high selectivity for the monoarylated amine product. As the substituents on the N-aryl ring of the NHC increase in size, selectivity for monoarylation increases and this is further enhanced by chlorinating the back of the NHC ring. Computations have been performed on the catalytic cycle of this transformation in order to understand the selectivity obtained with the different catalysts.     

Random Copolymers of 1,5-Dioxepan-2-one

ABSTRACT

Copolymers of 1,5-dioxepan-2-one (DXO) and e-caprolactone (?-CL), δ-valerolactone (δ-VL) or L-lactide (LLA) have been synthesized and characterized. High molecular weight copolymers were obtained using stannous-2-ethyl hexanoate as catalyst in bulk. Reactivity ratios for the copolymerization of DXO and δ-VL were determined at 110°C as r_VL=0.5 and r_DXO=2.3. At high conversion, depolymerization of δ-VL occurred, resulting in lower molecular weight and variations in the copolymer composition.

Physical properties, such as crystallinity and melting temperature of the DXO-copolymers proved to be strongly dependent on the choice of comonomer and on the molar composition of the copolymers. DXO appears to be incorporated into the poly-?-caprolactone (PCL) crystals and to some extent into the poly-δ-valerolactone (PVL) crystals, resulting in a more gradual decrease in crystallinity with increasing amount of DXO.     

On the Hydrostannylation of Aryl Propargylic Alcohols and Their Derivatives: Remarkable Differences in Both Regio‐ and Stereoselectivity in Radical‐ and Nonradical‐Mediated Transformations

Herein, we describe a highly regio‐ and stereoselective radical‐mediated and molecular‐oxygen (O₂)‐dependent hydrostannylation of phenyl propargylic alcohols and their derivatives. There is a significant steric effect on the stereoselectivity of the tin‐radical addition. Further, the uncatalyzed regio‐ and stereoselective hydrostannylation of aryl propargylic alcohols with nBu₃SnH and Ph₃SnH is also described and occurs with near titration kinetics. Although the uncatalyzed addition with nBu₃SnH gave a remarkable γ‐regioselectivity irrespective of the electronic nature of the aryl moiety, addition with Ph₃SnH appears to be driven by the electronic nature of the aryl alkynes.     

Enzymatic oxidation of para-substituted arenes: access to new non-racemic chiral metabolites for synthesis

A series of para-substituted benzene derivatives were subjected to whole-cell fermentation with Escherichia coli JM109 (pDTG601), an organism expressing toluene dioxygenase (TDO). Several compounds proved to be excellent substrates for TDO, including 4-bromo-phenylacetylene, 4-bromobenzaldehyde, 4-bromobenzyl alcohol and 4-bromo-allylbenzene. Some of the first para-functionalized diene diols produced using TDO, are useful substrates for further synthetic manipulations, including their use in the potential synthesis of complex natural products.