Double-beta decay Q values of 130Te, 128Te, and 120Te

The double-beta decay Q values of 130Te, 128Te, and 120Te have been determined from parent-daughter mass differences measured with the Canadian Penning Trap mass spectrometer. The 132Xe-129Xe mass difference, which is precisely known, was also determined to confirm the accuracy of these results. The 130Te Q value was found to be 2527.01(32) keV which is 3.3 keV lower than the 2003 Atomic Mass Evaluation recommended value, but in agreement with the most precise previous measurement. The uncertainty has been reduced by a factor of 6 and is now significantly smaller than the resolution achieved or foreseen in experimental searches for neutrinoless double-beta decay. The 128Te and 120Te Q values were found to be 865.87(131) keV and 1714.81(125) keV, respectively. For 120Te, this reduction in uncertainty of nearly a factor of 8 opens up the possibility of using this isotope for sensitive searches for neutrinoless double-electron capture and electron capture with positron emission.Comment: 5 pages, 2 figures, submitted to Physical Review Letter

1,1′-(Ethane-1,2-di­yl)bis­(1,4,7-triazonane)

In the centrosymmetric title compound (dtne), C14H32N6, two 1,4,7-triaza­cyclo­nonane (tacn, or 1,4,7-triazonane) moieties are linked together each at an amino position by a single ethyl­ene spacer. The mol­ecular packing is supported by pairs of inter­molecular N—H⋯N hydrogen bonds, which form R 2 2(22) ring motifs and link the mol­ecules into infinite chains running parallel to the a axis

Mass measurements near the rr-process path using the Canadian Penning Trap mass spectrometer

The masses of 40 neutron-rich nuclides from Z = 51 to 64 were measured at an average precision of $\delta m/m= 10^{-7}$ using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a $^{252}$Cf spontaneous fission source in a helium gas catcher, approach the predicted path of the astrophysical $r$ process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in $\beta$-endpoint measurements. Differences in mass excess from the 2003 Atomic Mass Evaluation of up to 400 keV are seen, as well as systematic disagreement with various mass models.Comment: 15 pages, 16 figures. v2 updated, published in Physical Review

Synthesis and characterisation of phosphorescent rhenium(I) complexes of hydroxy- and methoxy-substituted imidazo[4,5- f ]-1,10-phenanthroline ligands

Eight new fluorescent ligands (L1-L8) derived from the fused imidazo[4,5-f]-1,10-phenanthroline core, have been synthesised utilising a one-pot methodology. The ligands include two points of structural variety, allowing multiply-substituted aryl groups (including hydroxy and methoxy moieties) to be attached to the ligand core. The ligands L1-L8 are fluorescent (λem = 399–426 nm) and react with pentacarbonylbromorhenium to give coordination complexes of the form fac-[ReBr(CO)3(NˆN)] (where NˆN = L1-L8). The complexes were characterised using a variety of spectroscopic and analytical techniques, including single crystal X-ray diffraction studies on two examples. The rhenium complexes were all found to be luminescent, revealing classical 3MLCT emission at 579–587 nm in aerated solution with corresponding lifetimes in the range 149–166 ns

Measurement of radiative proton capture on F 18 and implications for oxygen-neon novae reexamined

Background: The rate of the F18(p,γ)Ne19 reaction affects the final abundance of the radioisotope F18 ejected from novae. This nucleus is important as its abundance is thought to significantly influence the first-stage 511-keV and continuum γ-ray emission in the aftermath of novae. No successful measurement of this reaction existed prior to this work, and the rate used in stellar models had been calculated based on incomplete information from contributing resonances. Purpose: Of the two resonances thought to provide a significant contribution to the astrophysical reaction rate, located at Ec.m.=330 and 665 keV, the former has a radiative width estimated from the assumed analog state in the mirror nucleus, F19, while the latter resonance does not have an analog state assignment, resulting in an arbitrary radiative width being assumed. As such, a direct measurement was needed to establish what role this resonance plays in the destruction of F18 at nova temperatures. This paper extends and takes the place of a previous Letter which reported the strength of the Ec.m.=665 keV resonance. Method: The DRAGON recoil separator was used to directly measure the strength of the important 665-keV resonance in this reaction, in inverse kinematics, by observing Ne19 reaction products. A radioactive F18 beam was provided by the ISAC facility at TRIUMF. R-matrix calculations were subsequently used to evaluate the significance of the results at astrophysical energies. Results: We report the direct measurement of the F18(p,γ)Ne19 reaction with the reevaluation of several detector efficiencies and the use of an updated Ne19 level scheme in the reaction rate analysis. The strength of the 665-keV resonance (Ex=7.076 MeV) is found to be an order of magnitude weaker than currently assumed in nova models. An improved analysis of the previously reported data is presented here, resulting in a slightly different value for the resonance strength. These small changes, however, do not alter the primary conclusions. Conclusions: Reaction rate calculations definitively show that the 665-keV resonance plays no significant role in the destruction of F18 at nova temperatures

A mechanochemical zinc-mediated barbier-type allylation reaction under ball-milling conditions

A ball-milling-enabled zinc-mediated Barbier-type allylation reaction is reported. Notably, running the reaction in this manner renders it effective irrespective of the initial morphology of the zinc metal. The process is operationally simple, does not require inert atmospheres or dry solvents, and is reported over a range of aldehyde and ketone substrates; a gram-scale process is demonstrated

12^{12}C+16^{16}O sub-barrier radiative capture cross-section measurements

We have performed a heavy ion radiative capture reaction between two light heavy ions, $^{12}$C and $^{16}$O, leading to $^{28}$Si. The present experiment has been performed below Coulomb barrier energies in order to reduce the phase space and to try to shed light on structural effects. Obtained $\gamma$-spectra display a previously unobserved strong feeding of intermediate states around 11 MeV at these energies. This new decay branch is not fully reproduced by statistical nor semi-statistical decay scenarii and may imply structural effects. Radiative capture cross-sections are extracted from the data.Comment: 4 pages, 7 figures, to appear as proceedings of FUSION 2011 conference at St-Malo, Franc

Synthetic routes, characterization and photophysical properties of luminescent, surface functionalized nanodiamonds

The functionalization of small diameter (ca. 50 nm) polycarboxylated nanodiamond particles using amide coupling methodologies in both water and acetonitrile solvent has been investigated. In this manner, the surfaces of nanodiamond particles were adorned with different luminescent moieties, including a green fluorescent 1,8-naphthalimide species (Nap-1), and a red emitting ruthenium(II) tris-bipyridine complex (Ru-1), as well as dual functionalization with both luminophores. Comprehensive characterization of the surface functionalized nanodiamonds has been achieved using a combination of dynamic light scattering, nanoparticle tracking analysis, transmission electron microscopy, X-ray photoelectron spectroscopy, zeta potential measurements, microwave plasma atomic emission spectroscopy and time-resolved photophysics. The tendency of the functionalized nanodiamonds to aggregate reflects the degree of surface substitution, yielding small aggregates with typical particle sizes ca. 150 nm. This is likely to be driven by the reduction of the zeta potential, concomitant with the conversion of surface charged carboxylate groups to neutral amide functions. The results show that luminescent nanodiamond materials can be synthesised with tuneable photophysical properties